Experienced and professional animal trainer provide their insights in answering this question :
A. A fungal or bacterial infection would be the most likely cause

How to Identify Common Pet Problems ?

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

Smooth black lesions on a dog`s skin are often caused by hyperpigmentation, a harmless darkening of the skin that can occur after chronic inflammation. Raised scabs can occur for various reasons, including parasites, allergies and infections.
These lesions usually indicate injury, infection, or disease and require an examination by a veterinarian to determine the underlying cause. Treatment and prognosis varies depending on the source of the ulcer. A skin ulcer is a deep lesion that can be caused by a variety of factors, ranging from bug bites to cancer.
Black Spots and Hyperpigmentation

These spots can come from aging, intense friction in one area, or even sun exposure. For the most part, hyperpigmentation could be harmless. As with anything, you`ll want to watch to see if new, unusual, or worrisome behaviors begin.

Ringworm characteristically appears in a circular or ring-shaped pattern on the skin, usually causing the skin to turn red, lose hair, and swell up. Ringworm in your dog may not present itself in such a noticeable manner, so you should keep an eye out for the following symptoms: Inflamed, red skin rash.
Ringworm can manifest itself in dogs in a variety of ways, most commonly as patches of hair loss with a crusty coating or (rarely) as asymptomatic. Ringworm patches in some dogs look like a grey, scaly patch, while others look like a scarlet lesion.
What does ringworm in dogs look like? In the dog, ringworm lesions usually appear as areas of hair loss (alopecia) that are roughly circular. As these circular lesions enlarge, the central area heals, and hair may begin to regrow in the middle of the lesion. The affected hair shafts are fragile and easily broken.
What does a cancerous lesion look like on a dog? Veterinarians advise the following signs. One may feel firm, raised wart-like blemishes that are squamous cell carcinoma. One may see rubber-like, inflamed sores that are mast cell tumors.
Skin ulcers typically look like a round open sore in the skin. The outer border of the sore might look raised and thick. As the ulcer forms, you may notice the skin discoloration in that specific area. It might begin to look red and feel warm.
Melanocytomas are non-cancerous tumors of the coloration skin cells. These dark mole-like blotches are generally found in the front half of the body and can come in a wide range of shape and sizes. Surgical removal is recommended.
Warts, caused by canine viral papilloma, and adenomas are one of the most common types of small lumps on dogs. These masses are benign, irregularly shaped like cauliflower, and usually pale in appearance. However, when they become inflamed or infected, blood or pigment can turn the bumps dark.
A scaly ring-shaped area, typically on the buttocks, trunk, arms and legs. Itchiness. A clear or scaly area inside the ring, perhaps with a scattering of bumps whose color ranges from red on white skin to reddish, purplish, brown or gray on black and brown skin. Slightly raised, expanding rings.
Itraconazole, terbinafine, and griseofulvin are the three most common medications prescribed to treat ringworm in dogs. If you have more than one pet at home, try to isolate the infected animal to prevent the disease from spreading. Provide him/her with their own room and a clean bed.
Ringworm — also known as dermatophytosis, dermatophyte infection, or tinea — is a fungal infection of the skin. “Ringworm” is a misnomer, since a fungus, not a worm, causes the infection. The lesion caused by this infection resembles a worm in the shape of a ring, which is why it got its name.
Ringworm looks similar on dogs and cats, and it can easily be mistaken for other types of skin infections, including skin allergies, dog dermatitis, and skin irritation. Ringworm is a type of fungal skin infection and typically doesn`t require treatment in healthy animals.
Ringworm on the skin starts as a red, scaly patch or bump. Over time, it may look like one or more rings with raised, bumpy, scaly borders (the center is often clear). This ring pattern gave ringworm its name, but not every infected person has it.
Ringworm typically begins as a flat, discolored patch, which may appear red in lighter complexions and brown in darker complexions. The patch has a ring-like or circular shape with a raised, scaly border.
Tumors are usually small lumps or bumps, but they also can occur as hairless, discolored patches, rashes, or nonhealing ulcers. Because skin tumors are so diverse, identifying them should be left to a veterinarian. Tumors may be benign or malignant (cancerous).
Basal cell tumors are benign growths that develop on the head, ears, neck, and forelimbs of older dogs. They are raised swellings that are typically firm, solitary, dome-shaped, and small. Some may be hairless, ulcerated, and stick out like stalks from the surface of the skin.
A bone lesion is considered a bone tumor if the abnormal area has cells that divide and multiply at higher-than-normal rates to create a mass in the bone. The term “tumor” does not indicate whether an abnormal growth is malignant (cancerous) or benign, as both benign and malignant lesions can form tumors in the bone.
Do not use rubbing alcohol or hydrogen peroxide as these can damage the tissue and delay healing. Cover up the wound with a bandage. Apply a small amount of antibacterial ointment and cover the wound with a piece of sterile gauze or other bandage. Use the elastic tape to hold the bandage in place.
Eschar is characterized by dark, crusty tissue at either the bottom or the top of a wound. The tissue closely resembles a piece of steel wool that has been placed over the wound. The wound may have a crusted or leathery appearance and will be tan, brown, or black.
A skin wound that doesn`t heal, heals slowly or heals but tends to recur is known as a chronic wound. Some of the many causes of chronic (ongoing) skin wounds can include trauma, burns, skin cancers, infection or underlying medical conditions such as diabetes. Wounds that take a long time to heal need special care.
They will also become much darker than the surrounding skin due to the amount of melanin that will end up being concentrated in just one area. However, while these growths are typically benign, they can sometimes result in a tumor developing, putting the dog at risk of cancer spreading into other parts of the body.
Dogs that develop melanoma tend to be older and the cause of melanoma is unknown in dogs. Most melanomas in the mouth or skin will present as dark, raised masses. Some melanomas may appear as a pinkish color (amelanotic melanomas).

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. My pom has a small sore with a perfect round black ring around it on her side. Don’t know how she got it. Just noticed it
ANSWER : A. A fungal or bacterial infection would be the most likely cause

Q. I have a 2 month old american pitbull and I don’t know what to feed him and I also got a 2 year old hevaneese and I don’t want to buy to diffrent food
ANSWER : A. Until your pitbull is fully grown, around 12 months, it is important that he has a puppy diet as it has the added nutrients necessary for healthy growth of bones, muscles etc and is higher in fat too. You do not want these added nutrients in an adult food as they can cause problems including obesity especially in your small breed dog. This means that unfortunately until your puppy has reached adulthood they will need different foods. When they are both adults they can have the same food although ideally they should be on a large breed and small breed diet respectively as they have different needs. Larger dogs tend to suffer from joint problems so the large breed diets will have supplements in them to help with this.

Q. Got my dog 5 yrs. ago and her previous owner died! Since then we can’t find her old vet so we don’t know her info! I don’t even know her age. Ideas?
ANSWER : A. Do you know her name? You could possibly call the vets in the local area and ask if they have her on file. The only issue with that is they may have legal issues releasing any information to you due to privacy reasons. The only thing you’re probably going to be able to do is start over and pretend she’s not up to date on her shots at your next visit. The doctor will probably just start doing an annual round of shots such as DHPP (Distemper/Parvo), Rabies, Kennel Cough, and possibly some others like a vx for Lepto and/or Lymes.

Q. My cat is throwing up and it’s a bright yellow liquid,we don’t know if he got into something or if something serious going on.we need to know .
ANSWER : A. If the vomiting is accompanied by diarrhea, lethargy or loss of appetite then you should see your vet. If she seems otherwise “normal”, withhold food for 12-24 hours. Allow small amounts of water or unflavored PediaLyte. Resume feeding a bland diet (1:1 ratio of plain boiled boneless chicken and plain white rice). Feed in small, frequent amounts waiting at least one hour between feedings. If the vomiting stops, transition slowly to the regular diet. If not or you see other symptoms, see your veterinarian.

Q. I have an apricot poodle. I’ve noticed the left side of his nose has a black spot and is swollen. It opened and puss oozed out. What could be the caus
ANSWER : A. This could be an infection or it could be a growth with has got infected. I advise you get a full check up by your vet, a small sample can be taken to identify the nature of the lump and to guide most appropriate treatment

Read Full Q/A … : chianti.ucsd.edu

Q. Our 6 yr old Pitt retriever mix got a small mast cell tumor removed from her chest 3 days ago. Today she has a rash near the incision site, thoughts?
ANSWER : A. Mast cell tumors tend to release histamine to the tissues around the tumor, sometimes that can cause itchiness and rash around the wound, even bleeding called Darier’s sign. If they removed enough tissue around the tumor calm down and go tomorrow to your vet that possibly will give you some tablets to improve that reaction, normally steroids.

Q. One of my pet’s ears seems very irritated. What I can use to clean it with?
ANSWER : A. Ear Irritation can be caused by a number of things ranging from allergies, ear infections or even mites. Dirty ears can also cause irritation and problems. Knowing the type of problem is best for figuring out how to treat it.

For plain dirty ears that do not have any odor, redness or leakage of discharge/debris, a simple over the counter canine ear cleaner can be used. Gently soak some cotton balls or a washcloth with the cleaner, and then use these to wipe out the flap of the ear and opening to the ear. Do NOT use Q-tips as these can become stuck or lodged in the curve of the ear canal and may cause injury to the ear drum.

If the ear is bright red or itchy without any dirt or debris in it, it may indicate an allergy. Sometimes an allergy medication can help provide relief in this situation. Your vet can give you the correct dosages of an over the counter allergy medication to use, or may recommend one specifically for dogs.

For infections and mites, changes to the ear such as bad smell or lots of debris and discharge, flecks of black or brown debris, or scabs and sores in the ear may be present. In these cases, it is best to have your vet take a sample of the ear debris to test for mites or infection. Your vet can then give you an ointment that is placed and left in the ear between ear cleanings. Most vets will then recommend cleaning the ears twice daily and then leaving in the ointment after for a period of ten days.

Ear mites ARE contagious to other pets, so if your dog does have them, it is best to treat any other pets in the house at the same time to prevent the mites from spreading around continuously.

Q. Our small puppy had a black widow in her mouth, but seems not to have been bitten. Could she have been bitten and we just don’t know it yet?
ANSWER : A. If she was bitten, you might see swelling, drooling or lethargy, muscle spasms, difficulty breathing or ataxia (wobbly gait). There may also be redness. The venom of a black widow spider can easily kill a small dog, or induce severe reactions in young dogs. Monitor her closely but seek veterinary attention if you think she was indeed bitten.

Read Full Q/A … : Black Widow Spider