Experienced and professional animal trainer provide their insights in answering this question :
A. If your pet is not spayed or was spayed after 1-2 years of age there is a chance that this swelling could be mammary cancer. Mammary cancer in pets is common and the chances of cancer are decreased an the risk of getting cancer is only 0.5% if spayed before the 1st heat cycle, 8% if spayed before the 2nd heat cycle, 26% if spayed by the 3rd heat cycle. After the 3rd heat cycle spaying a pet will not decreased chances of mammary cancer.
I would highly advise that you take your pet tot he vet to have this area examined. Typically mammary cancer lumps are firm and can be on multiple breasts.
Without seeing the lump myself, another possibility here is a lipoma (soft fatty tumor) or an abscess.

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

How is mastitis treated? Most dogs with mastitis can be treated on an outpatient basis with oral antibiotics and pain medications. This treatment is ideal, as it allows the dog to remain at home with her puppies. Your veterinarian may recommend hand-milking the infected gland.
Cabbage leaves help to reduce pain and inflammation. Your veterinarian will advise you to wrap two cabbage leaves together and apply them to the affected breasts like a compress, changing them every few hours. Perform hand milking of the affected breasts as often as your veterinarian recommends.
Timely treatment of mastitis in dogs will stop the infection from spreading and reduce the damage caused by the infection. If the infection is mild, early treatment at home will help reduce pain. For example, you can apply warm compresses to the mammary glands. For warm compresses, you can use cabbage leaves or towels.
When to contact your vet. It`s important to get your dog checked by your vet if you notice any changes to their mammary glands, especially if you notice any redness, swelling or new lumps.
Swollen nipples in dogs is a common sign seen in mastitis. Mastitis occurs when there is an infection of the mammary glands. Mastitis can occur in female dogs who are in the process of nursing. In mastitis, the dog`s mammary glands become swollen and painful.
It is normal for a dog`s nipples to remain enlarged for a couple of weeks following the heat cycle. It is a result of hormonal changes that occur during the cycle.
Mastitis treatment

Sometimes breast infections go away on their own. If you notice you have symptoms of mastitis, try the following: Breastfeed on the affected side every 2 hours, or more frequently. This will keep your milk flowing and prevent your breast from getting too full of milk.

Antibiotics. If you have an infection, a 10-day course of antibiotics is usually needed. It`s important to take all of the medication to minimize your chance of recurrence. If your mastitis doesn`t clear up after taking antibiotics, follow up with your doctor.
Mastitis usually only affects 1 breast, and symptoms often come on quickly. They include: a swollen area on your breast that may feel hot and painful to touch – the area may become red but this can be harder to see if you have black or brown skin. a wedge-shaped breast lump or a hard area on your breast.
Cephalexin (15–30 mg/kg, PO, every 8 hours) and amoxicillin/clavulanate (14 mg/kg, PO, every 8–12 hours) are recommended as initial therapeutic agents pending culture results. Hot-packing the affected gland encourages drainage and seems to relieve discomfort.
The beta lactamase-resistant penicillins have been recommended in the treatment of mastitis. These include cloxacillin, dicloxacillin, or flucloxacillin. Because penicillins are acidic, they are poorly concentrated in human milk, which is also acid.
The average survival time for mammary gland sarcomas of any kind is short, usually between 9 and 12 months. Inflammatory mammary gland tumors are highly aggressive and typically present as a rapidly growing tumor with ulceration, edema and erythema.
The fall of progesterone triggers a rise in prolactin, a mammary-stimulating hormone. It`s normal for dogs at this stage to have swollen nipples, even when there is no pregnancy.
For many, as their body heals and recovers, their swelling usually disappears with time. However, some women do experience persistent swelling in the area. Here are 5 ways to reduce and manage breast and chest wall swelling. The best way to reduce swelling is with the use of a compression bra or tank top.
Enlarged or Discolored Nipples

While a female dog`s nipples are normally small, pregnancy causes her nipples to grow in size during the early stages of pregnancy. The areolas also become somewhat rounded compared to their usual flatness.

People have been using vinegar on nipples for ages to help them shrink back. If your dog`s nipples are sore from all the nursing, vinegar can also provide relief. Just make sure to use it after the puppies are weaned. Another idea is to put your dog in a swimsuit.
As mastitis progresses, the infected mammary gland will become increasingly swollen, inflamed, discolored (frequently red or purple), and painful. The mammary glands also may become ulcerated, with open wounds and scabs visible on the mammary gland.
Your healthcare provider will prescribe an antibiotic to treat a bacterial mastitis infection. They work to eliminate the bacterial infection that`s built up in your milk ducts. The infection should clear up within 10 days. However, you should begin to feel relief within 48 to 72 hours.
Use cold to reduce the swelling.

Swap it every 20-30 minutes, when it`s no longer cold. Older advice often suggested using heat, but we now know that this can make the inflammation worse. It`s important not to handle your breast roughly, as this can make swelling worse (and will hurt!).

Another good remedy for mastitis is garlic, which has natural antibiotic properties. It helps get rid of the bacteria causing the infection. In addition, it boosts the immune system and promotes quick recovery.
In some cases, using the tips below can help mastitis clear up in a day or two—but some infections that don`t resolve on their own need to be treated with an antibiotic.
Avoid saturated fats

Limit your intake of saturated fats to prevent blocked ducts (fried foods, bakery food, vegan cheese and margarines) and include foods naturally containing some lecithin like peanuts, wheatgerm, soy, cooked green vegetables and wholegrains.

There is a chance that mastitis occurs in a dog even if they aren`t pregnant or nursing. In this case, it may be caused by cancer of the mammary glands, which would require immediate medical attention from a vet.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. Whenever I take my dog on walks he always barks at people and others dogs in my neighborhood. What should I do to resolve the problem
ANSWER : A. The very first thing to do is to make sure your dog is getting sufficient physical and mental exercise every day. A tired dog is a good, happy dog and one who is less likely to bark from boredom or frustration. Depending on his breed, age, and health, your dog may require several long walks as well as a good game of chasing the ball and playing with some interactive toys.

Figure out what he gets out of barking and remove it. Don’t give your dog the opportunity to continue the barking behavior.

Ignore your dog’s barking for as long as it takes him to stop. That means don’t give him attention at all while he’s barking. Your attention only rewards him for being noisy. Don’t talk to, don’t touch, or even look at him. When he finally quiets, even to take a breath, reward him with a treat. To be successful with this method, you must wait as long as it takes for him to stop barking. Yelling at him is the equivalent of barking with him.

Get your dog accustomed to whatever causes him to bark. Start with whatever makes him bark at a distance. It must be far enough away that he doesn’t bark when he sees it. Feed him lots of good treats. Move the stimulus a little closer (perhaps as little as a few inches or a few feet to start) and feed treats. If the stimulus moves out of sight, stop giving your dog treats. You want your dog to learn that the appearance of the stimulus leads to good things.

Teach your dog the ‘quiet’ command. Oddly, the first step is to teach your dog to bark on command. Give your dog the command to “speak,” wait for him to bark two or three times, and then stick a tasty treat in front of his nose. When he stops barking to sniff the treat, praise him and give him the treat. Repeat until he starts barking as soon as you say “speak.” Once your dog can reliably bark on command, teach him the “quiet” command. In a calm environment with no distractions, tell him to “speak.” When he starts barking, say “quiet” and stick a treat in front of his nose. Praise him for being quiet and give him the treat.

As in all training, always end training on a good note, even if it is just for obeying something very simple, like the ‘sit’ command. If you dog regresses in training, go back to the last thing he did successfully and reinforce that before moving on again. Keep sessions short, 15-20 minutes max, and do this several times a day.

Q. How do I determine how much my overweight pet should weigh?
ANSWER : A. There are many tools to determine overweight and obesity levels in pets. A new tool, morphometric measurements and body fat index, are available to accurately determine a pet’s ideal weight; this will allow an accurate determination of the amount of food a pet should receive to achieve weight loss. Feeding the correct amount will lead to greater weight loss success.

There are many weight loss food options to help pets reach their ideal weight. Your veterinarian can help make a ideal weight recommendation. Here are some tips to help your dog lose weight in a healthy and safe way:

1. Diet: Providing a healthy and well balanced diet is essential to your pet’s overall health. Finding the right food for your dog can be a challenging process. For those overweight animals many commercial dog companies offer weight loss diets, but it is important to evaluate food labels for adequate nutritional content.

You want to ensure you are not missing other essential vitamin or mineral content. Volume of food is also important and the amount of food that works for one breed of dog may not be the same for another breed of dog. Portion control as opposed to free-choice feeding can help your dog to drop a few unnecessary pounds.

There are also prescription weight loss foods designed by veterinary nutritionists, such as Hill’s r/d (http://bit.ly/1AoENSd). Some pet owners find that home cooking is the best option for helping to provide a well-balanced and realistic diet plan. There are websites such as balanceit.com that offers recipes to fit your dog’s specific needs. Consulting with your veterinarian or a veterinary nutritionist to find the appropriate diet is a great way to help your dog be as healthy as possible.

2. Exercise: Another great tactic for weight loss for your dog is exercise. Whether this is through running, walking or playing with a favorite toy all of these are wonderful types of exercise to help keep your dog at a lean and healthy weight.

For those pet owners with busy schedules utilizing professional dog walking services or playtime through dog daycare services is another option. It has been shown that those pet owners that exercise regularly with their pets generally live a healthier lifestyle.

3. Physical therapy: As animals age pet owners offer encounter their favorite canine having more difficulty walking and have a dwindling desire to play with toys. Physical therapy, specifically hydrotherapy is a wonderful way to help older and arthritic animals gain more mobility and lose weight. Hydrotherapy has been proven to have several therapeutic effects on the body including, muscle strengthening, relief of swelling, decreased joint pain, less stiffness in limbs, improved circulation, weight loss, and increased tissue healing to name a few. For more information on the benefits of hydrotherapy:
http://bit.ly/1w1qqoy

4. Veterinary visit and blood work: Weight gain can also be related to underlying health concerns such as hypothyroidism or other endocrine disorders. Scheduling a veterinary evaluation and routine blood work can be another important component in increasing the longevity of your dog’s life. Conditions such as hypothyroidism that predispose dogs to gain weight can be treated with a daily medication to improve hormonal balance. If feel that your dog is unnecessarily overweight there can be an underlying health condition that needs to be addressed.

5. Healthy treats: Pet owners love the chance to reward their favorite canine companion with treats and most dogs jump at the chance to consume these delicious products. The problem is many treats, which can include commercial dog treats or table scrapes can add many unnecessary calories to your dog’s daily intake. Reading labels and making note of the calories in these treats is an important component of understanding your dog’s overall health. Treats should not exceed more than 10 percent of your pet’s daily calories. There are healthier treats that can be offered to your pet to keep calories lower yet provide a fuller sensation. A pet owner can add steamed or pureed vegetables, such as carrots, green beans or sweet potato to add more fiber and thus a fuller feeling for your dog.

Q. Rescued a dog almost two weeks ago, and now that her kennel cough is gone her personality shines!! No previous training, how should I start?
ANSWER : A. POST FOUR:

After your dog is familiar with the behavior you lured from scratch, and taught to your dog, you can start to use the “no-reward marker” I talked about. What you do is ask the dog to perform the behavior, and if the dog does not perform the behavior, you simply say your no-reward marker (choose one: eh-eh, hey, uh-oh, oops) show them the treat, put it behind your back, and BRIEFLY ignore your dog. Just turn your back for a second or two, before turning back to your dog and saying, “let’s try that again.” When you’re ready to start over with your dog, make sure you move around. If you are repeating the same cue while in the same position, while your dog is in the same position, you are likely to receive the same results. The more you move around, and start fresh, the better your chances are of having your dog listen to your cue the second time around. BIG rewards when they dog it successfully! Lots of praise and treats.

My no-reward marker is “hey.” When my dog does something wrong I say, “hey” and she immediately understands that she needs to offer a different behavior. This is clear to her. I don’t have to say it in a mean way, I simply say, “hey” in a normal tone of voice and she understands what the word means.

Once you’ve built up that connection and communication with your new dog, you can work on all kinds of fun behaviors! I personally enjoy the more zen-like behaviors: https://www.youtube.com/watch?v=ruy9UMcuGh8

I like to teach my dog fun tricks that offer her a “job” to do of sorts like object retrieval: https://www.youtube.com/watch?v=I4iertZSva8

(object retrieval training completed; what it looks like: https://www.youtube.com/watch?v=jx0Dml28FGY)

Scent-games are fun too! Very confidence building. Hide a REALLY smelly treat in a box, and place that box in a line of boxes. Let your dog go in the room while saying something like “search!” or “find it!” and watch them hunt for that smelly treat! Lots of rewards when they find it!

Q. My Beagle listens to me, but cries & whines when I’m gone & doesn’t listen to my parents. I adopted him just a couple days ago. Any tips for my folks?
ANSWER : A. I really highly doubt that your Beagle listens to you and has formed a connection with you in just a couple of days. It takes months to build up any kind of serious connection with your dog. You need to work on communication with your dog through training them to understand different cues. For instance the Leave-It cue: https://www.youtube.com/watch?v=R1TS5nA7z5Q

You have to work on bonding with your dog through mental stimulation. Training is very important. Luring each new behavior from scratch, and training using treats is how you form a strong bond with your new dog. No scolding is ever necessary… work on being calm, and positive, all the time.

If your dog is crying/whining when you leave, this may be separation anxiety. You’re going to have to separation train this dog from scratch. This dog needs to learn that separation can be a good thing! Tell your “folks” to NOT scold the dog when he is crying/whining after you leave, because that will make your dog MORE anxious when you leave next time. Your dog will be dwelling on the negative if your parents fuel your dogs negative feelings towards you leaving. FUN things should happen when you leave. Your parents should pull out the treats and start doing some basic obedience training with your dog. Your parents should stuff a Kong filled with awesome treats (peanut butter) and give it to him so he feels happy when you leave.

I have some excellent separation anxiety exercises you can work on. If you’d like, you can purchase a consultation with me, and I will go over how to separation train from scratch. It will make your dog comfortable being alone, guaranteed.

Read Full Q/A … : I Don't Like My Mother

Q. Why does my dog eat grass?
ANSWER : A. As another user mentioned, dogs can eat grass when they want to vomit. Sometimes, when a dog has an upset tummy, they will eat grass. If you notice your dog eating grass frantically, you can assume vomiting will shortly follow. Grass does not digest and pass normally. If your dog eats too much grass, it can cause serious issues with pooping. Your dogs poop can end up all tangled inside of her, and it can need veterinary assistance to remove it. The same goes for celery, so avoid feeding celery to your dog.

The other day my boyfriend accidentally left the laundry room door open where we were keeping the trash that was filled with cooked chicken bones. She ate one of the chicken bones lightning fast. We had to induce vomiting by feeding her some hydrogen peroxide. After we had fed her the peroxide, she immediately began frantically eating grass because her tummy was upset.

If there is something lacking in your dogs diet, it could be that your dog is eating grass to make up for it. I am sure that my dogs diet is extremely well balanced (I do not only feed her an air-dried raw food-type diet (Ziwipeak), but a wide variety of safe, healthy foods), so when she eats grass, I know that it is because she has an upset tummy.

That is why I think it is important making sure your dog has a very well balanced diet. If your dog is on a low quality kibble, your dog may be trying to let you know by eating grass (or eating poop).

Q. How do I desensitize my dog to squirrels and stray cats in the neighborhood?
ANSWER : A. It depends on the goal that you have in mind. I am going to assume that you would prefer that your dog not chase squirrels or stray cats in the yard/street. In this case, your options include: (1) training your dog on a “Leave it ” cue using positive reinforcement methods, (2) training your dog not to pull on its leash when it sees a squirrel/stray cat, and (3) training your dog to perform a more desirable behavior when it sees a squirrel/cat.
Training your dog on a cued “leave it” command is useful because it will give you the ability to tell your dog to stay away from any number of undesirable objects on your command. Training your dog to perform a more desireable behavior when it sees a squirrel or cat will substitute a behavior you find acceptable (sitting, laying down, coming to the door, etc.) with a behavior you dislike. Your dog can still react, just in a positive way. If your dog pulls on the leash every time you see a squirrel/cat, training not to pull will make your walk safer and more pleasant.
The ideal training method to use with dogs, or any animal for that matter, is positive reinforcement training, particularly a method called “clicker- training.” The basic concept of positive reinforcement training is to pair a reward (reinforcement) with a behavior you want to increase in frequency. In other words, when your dog performs the behavior you desire, it receives an award, which reinforces the desired behavior so you get more of that behavior. There are many excellent books in stores or on-line that describe positive reinforcement training in detail and many give step-by-step instructions for training common commands like “leave it”. Look for books that specifically mention positive reinforcement training or clicker-training. You can also take dog training classes to learn the techniques, find a mentor who already uses clicker-training, or request a consult from one of the pet experts on this site to guide you.

Q. What can I do to stop my dog from barking at people and front doors?
ANSWER : A. Ignore your dog’s barking for as long as it takes him to stop. This means don’t give him any attention at all while he’s barking. Your attention only rewards him for being noisy. Don’t talk to him, don’t touch him, and don’t even look at him. When he finally quiets down, even to take a breath, reward him with a treat. To be successful with this method, you must wait as long as it takes for him to stop barking. If he barks for an hour and you finally get so frustrated that you yell at him to be quiet, the next time he’ll probably bark for an hour and a half. Dogs learns that if they bark long enough you’ll give them attention.

Teach your dog the ‘quiet’ command. It may sound nonsensical, but the first step is to teach your dog to bark on command. Give your dog the command to “speak,” wait for him to bark two or three times, and then stick a tasty treat in front of his nose. When he stops barking to sniff the treat, praise him and give him the treat. Repeat until he starts barking as soon as you say “speak.” Once your dog can reliably bark on command, teach him the “quiet” command. In a calm environment with no distractions, tell him to “speak.” When he starts barking, say “quiet” and stick a treat in front of his nose. Praise him for being quiet and give him the treat.

When your dog starts barking, ask him to do something that’s incompatible with barking. Teach your dog to react to barking stimuli with something that inhibits him from barking, such as lying down in his bed.

Make sure your dog is getting sufficient physical and mental exercise every day. A tired dog is a good dog and one who is less likely to bark from boredom or frustration. Depending on his breed, age, and health, your dog may require several long walks as well as a good game of fetch and playing with interactive toys.

Q. My 4 yr old male Catahoula Leopard Dog mix is a rescue. He’s become very possessive of me around larger dogs. How can I correct this behavior?
ANSWER : A. Sudden behavior changes can sometimes indicate an underlying health issue, so scheduling a checkup with your regular vet is always the first step. Once any health issues have been addressed, then you can address the behavioral ones. It is very common for dogs to become “possessive” of people or objects when around other dogs or people, and is called location guarding. Possession of objects or places can be a little easier to manage, however possession around other dogs can be treated as well. Working from a distance in a technique called BAT or Behavioral Adjustment Training may help. This technique involves your dog and another calm dog. Start off at a far distance and then move in until your dog becomes reactive or wary of the other dog. Move back a small amount and wait for your dog to become calm. If he shows calm behavior, reward with lots of praise, treats and love! If he becomes agitated or possessive, move back until he is calm, or stop the session completely and try again later. While this may take some time, it can help dogs learn that other dogs are not a threat to them or their people. Reading more information about BAT training or contacting a local trainer in your area can help with further advice and techniques!