Experienced and professional animal trainer provide their insights in answering this question :
A. It sounds like your dog may have had a seizure. Please have her seen by a veterinarian to determine why this may have happened. Seizures can be caused by neurological conditions, toxicities, etc.

How to Identify Common Pet Problems ?

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

Potential causes include inner/middle ear infections, intoxication, strokes, tumors, infectious or inflammatory diseases (meningitis), idiopathic vestibular disease (also called “old dog” vestibular syndrome), or other less likely causes.
When your dog doesn`t feel safe, surges of adrenaline help to prepare their body to either defend itself or run away from danger. As adrenaline floods through their system it gets their muscles ready for action and often causes them to shake or tremble.
Neurological conditions such as seizures, viruses (such as Distemper) can cause your dog to act scared and shake. Neurological conditions cause involuntary shaking and seizing which can be very scary for your dog and cause them to show fear and to shake uncontrollably.
My dog is walking sideways and falling over; what`s going on? A few reasons your dog may be walking sideways are injury, hip dysplasia, and vestibular disease. If your dog has started to walk sideways, it`s best to have him evaluated by a veterinarian for an underlying condition.
What is Disorientation? Disorientation can occur acutely, or develop and worsen over time depending on the cause. You may notice that at times, or consistently, your dog is developing what seems to be a struggle to maintain a balanced position, or perhaps all of a sudden his eyes cannot focus and dart back and forth.
Disorientation. When you see your dog confused or even panicking, this can be a sign of nervous system disease. Regardless of age or breed, disorientation, head tilt, and loss of balance might all be related to the vestibular system in dogs.
Common Signs of Dog Poisoning

The following may be signs of dog poisoning: Diarrhea or blood in the stool (either bright red blood or dark black tarry stools) Vomiting or loss of appetite. Seizures or tremors.

Lack of Socialization

Puppies that don`t have positive exposure to the world around them might be more likely to be wary of anything new or unusual. This can lead them to be scared of things we wouldn`t associate with fear, like people wearing large hats or having a stroller/skateboard/skater go past you.

Shivering and trembling may be symptoms of something serious — like poisoning, kidney disease, or injury. So, if your dog suddenly starts trembling or shivering, it`s important to take note of other symptoms such as diarrhea, vomiting, or limping. Then talk to your vet right away.
If your dog is staggering, stumbling, or falling over, it could be the result of a number of medical issues, including injury, stroke, poisoning, or an infection.
Strokes can affect how your pet controls their eyes. Look out for abnormal eye movements such as your dog`s eyes constantly rotating or darting from side to side. Furthermore, one eye may stay still while the other moves, or both your pet`s eyes may look as though they are focusing on two different spots.
Many mobility issues can cause a dog`s hind legs to give out and collapse underneath them suddenly. For example, a dog`s back legs can collapse due to an injury, leg weakness in an older dog, arthritis, or a more serious health condition such as Degenerative Myelopathy.
Water on the Brain

Hydrocephalus occurs when fluid builds up inside the skull, putting pressure on the brain. This condition is most common in breeds with dome-shaped heads, like your Chihuahua. Hydrocephalus most often occurs when the skull bones don`t fuse properly after birth.

Shivering could be a sign that your dog is in pain or suffering from an illness. Shivering and muscle tremors can be symptoms of serious conditions such as distemper, hypoglycemia, Addison`s disease and inflammatory brain disease, as well as more common ailments like an upset stomach.
Anxiety. If your dog is afraid of loud noises, like thunder or fireworks, they may react by shivering and shaking. It`s not uncommon for dogs to have anxiety, especially when major environmental changes happen in `their space`. If your dog`s anxiety is severe enough then you may want to contact your veterinarian.
Symptoms caused by swallowed poisons can include: vomiting, diarrhoea, agitation and heart issues. Inhaled toxins may cause breathing difficulties or loss of consciousness in dogs. If your dog`s skin comes in contact with a poisonous substance typical symptoms include irritation and pain.
Affected dogs show signs 30 minutes to 4 hours after ingesting the poison. Initially affected dogs become anxious and have an elevated body temperature. Panting is usually seen. Progressively they become worse and staggery.
Poison Control

Consider using hydrogen peroxide (one teaspoon per five pounds of body weight), to induce vomiting. Dr. Putter advises using hydrogen peroxide (which is a gastric irritant) under consultation with animal poison control.

If your pet just gobbled up poison, the treatment may begin by making your pet vomit. Your veterinarian will tell you whether or not to induce vomiting based on what your pet ate. Your veterinarian will explain how to get your pet to vomit using salt water, dilute hydrogen peroxide, or Ipecac.
One of the most common treatment options for poisoning in dogs is inducing vomiting. Other treatment may include medication to reduce pain and symptoms, overnight monitoring, or IV`s for flushing out the toxins in the system. The cost of treatment can vary from $250 to $5,000.
Try a Thundershirt – This snug shirt wraps around your dog and applies gentle, constant pressure, similar to swaddling a baby. It can sooth some dogs into a calmer state. Supplement the scary sounds with music, TV, or white noise. Some certified veterinary behaviorists say classical music works magic on scared pets.
Toy breeds, in particular, tend to shake and tremble more than other types of dogs; this especially happens with Chihuahuas. “This can be due to their small size, so they tend to feel colder than larger dogs do, and this can cause them to shiver,” explains Dr. Barrack.
Symptoms can include collapsing, jerking, stiffening, muscle twitching, loss of consciousness, drooling, chomping, tongue chewing, or foaming at the mouth. Dogs can fall to the side and make paddling motions with their legs. They sometimes poop or pee during the seizure. They are also not aware of their surroundings.
Monitor your dog for several days.

Sometimes, dogs appear normal after a fall as they walk around and play. Later, they become lethargic and weak or develop difficulty breathing, so it is important to monitor them closely for several days after a fall.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. My 6yr old female chihuahua (un-spayed) just slowly fell over,slightly shaking and was disoriented..what could be wrong?
ANSWER : A. It sounds like your dog may have had a seizure. Please have her seen by a veterinarian to determine why this may have happened. Seizures can be caused by neurological conditions, toxicities, etc.

Q. We have a 3 yr old Weiner dog, she is having pus in her eyes, I took her to the vet he gave me derma vet ointment, used it as the doctor prescribed
ANSWER : A. If the pus really isn’t all that bad, and it’s just some discharge, your pup may benefit from a diet change. It could be that the food you’re feeding just isn’t right for your dog, and that’s okay! Dogs grow and change over time, and now that your dog is fully matured, a diet change may be in order. Try something like Taste of the Wild, maybe a grain free dog food, Orijen, or Ziwipeak. These are all really great food options.

If the pus is really bad, and continues to get worse, see your vet again and let them know what’s going on. Maybe you could try a diet change, and then see if there are any improvements.

Remember, you should always gradually change a dogs diet. By gradually, I mean you put a tiny bit of new kibble in with a bowl of the old kibble. Reduce the old kibble by just a few bits of kibble. Throughout the course of at least two weeks (or as long as you want depending on whether or not you want to finish off the old food) you slowly add more of the new kibble while removing some of the old kibble. This makes the process gradual, and won’t cause any tummy-upset in your dog.

Q. My 5 month old dog woke up today very lethargic and not very hungry. His feces smells very bad and it has an orange colored mucus in it. only 5 lbs
ANSWER : A. This could be many things, however first I’d ask you (if we could talk) if your puppy is vaccinated against parvo? That’s a serious viral disease that produces very bad-smelling bloody diarrhea. If he’s not vaccinated against parvo, please take him in to see a vet right away.

Otherwise, if he is vaccinated against parvo, he could have intestinal parasites, he could have eaten something that’s upset his GI tract, or he could have a bacterial infection, for starters. The orange color you mentioned has me especially concerned – I’m worried it could be blood. Regardless – he’s not eating, and he’s lethargic, so he likely feels pretty awful. I recommend you take him to see a vet right away who can figure out what’s going on and treat it appropriately.

Read Full Q/A … : Causes of Blood in Dog Stool

Q. My 4 year old Chihuahua mix began having a series shaking/panting episodes (last 15m- 1hr) out of the blue. Vet’s tests say its not physical.
ANSWER : A. There are many causes for shaking/panting. The shaking and panting are both signs of stress, and your dog may be dealing with anxiety, or stress, related to an event that happened, or is happening. I realize you cannot answer questions on this, however, I will ask some questions that you can ask yourself. Have you recently moved? Have you ever hit or yelled at your dog? Has the weather been bad lately (storms)? Have you had any new guests stay over recently? Have you had any dogs come to your home recently? Have you had any dogs or cats in your yard recently? Was your dog frightened by something initially (a falling pot/pan; a loud bang from the washing machine; a gunshot; a backfiring car/truck; someone screaming in your home/a fight)?

If you answered yes to any of those questions, it could definitely be that. Dogs don’t typically hang on to something for very long, but if it really frightened your pup, then she/he could be feeling serious anxiety related to that specific event, and relating other events to that one.

Do not yell, or hit your dog. I’m not assuming you do, but if you do, please stop doing that right away. It could be that your dog is afraid of you specifically, and you notice the shaking/panting when you are near, because that is the only time your dog is doing it.

If you’d like to purchase a consultation with me (I know, it’s a lot to ask, but I really feel like I could help) I’d be more than happy to ask you many questions, and together we can figure out what the heck is going on here. It’s important that your dog is comfortable, and if your pup is always feeling anxious/uneasy, then his/her quality of life is in jeopardy.

Q. My dog is bleeding out of rearend after
going to vet for a leg trouble the vet says
it is stres
ANSWER : A. It could be many things causing the problem. If it is an unneutered female it could be a season, if it is in the urine it could be a cystitis which could be set of by stress amongst other things. It could be from the anal glands or it could be from the lower intestinal tract. If it is the latter I would be careful what pain relief medication you are giving as some can cause bleeding in the GI tract such as meloxicam. I would recommend having a recheck with your vet to establish where the bleeding is coming from as some causes may require treatment or a change in current treatment.

Q. My dog has had dark red blood in stools for 2 days now . She found & ate a baby bird back in August , could that cause a problem now after so long
ANSWER : A. It seems pretty unlikely to me that the bird ingestion could have anything to do with the blood in the stool you’re seeing now. Depending on exactly how it looks, it could be a number of things. If the stool is normal and has blood on it, it could be an anal gland problem (infection, tumor) or a problem inside the rectum, like a mass. If she’s got diarrhea along with blood, she could have a bacterial or parasitic infection in her intestines, or she could have inflammatory bowel disease. I’d get this checked out as soon as possible.

Read Full Q/A … : Causes of Blood in Dog Stool

Q. My dog ran away 3 days ago , he came back later and immediately threw up all his food. He hasn’t eaten and is still throwing up since then.
ANSWER : A. I’m really glad to hear your dog came back! If you dog is vomiting I would recommend having him examined by a veterinarian because his vomiting could be caused by a gastrointestinal disturbance. He could have eaten something that upset his stomach, including an intestinal parasite or he could have even consumed something toxic. It would helpful for a veterinarian to evaluate for any injuries he could have sustained while being out of the home and for any abnormalities that could be causing his sickness. Stress could also be playing a role in his stomach upset since he was out of the home for several days.

Q. Change 10 week old Chihuahua puppy food, breeder food not available. Now Chihuahua puppy has loose stools. What can I do? Pumpkin?
ANSWER : A. Pumpkin can help. If you changes food abruptly rather than gradually adding more of the new food with the old eventually phasing out the old, that could be why puppy has loose stools. He may need more time to adjust. I would also look into fecal samples being tested at the vet in case he may have parasites as well.

Read Full Q/A … : Leerburg