Manifestations of Allergies in Domestic Animals: What Behavior Consultants Should Know

Written by Jess Elliott

When you meet a client and their animal for the first time, your evaluation can be made more comprehensive by recognition of outward and behavioral signs of disease. Physical problems affect both the animal and the interaction between the animal and their family, so a complete picture always includes a medical history. By recognizing issues the client may not be aware of, the behavior consultant can encourage the client to address underlying factors that may be causing distress.

There are two important aspects to the information below. The first, for professionals involved in behavior, is to help you recognize less common signs of allergy that can negatively affect the behavior of the animal you’re evaluating, and ones that seem behavioral but may instead have an important physical component. Head bobbing in horses, air-licking in dogs, and overgrooming in cats come to mind. The second is that animals may not show signs of suffering that are recognizable to the clients. Educated observers also have a duty to advocate for animals; a big part of that advocacy is to help their families learn to read them.

Some signs of allergy that we see in multiple species

The reverse sneeze (aka inspiratory paroxysmal respiration): This is a potential sign of inhaled allergy or irritants in dogs and, less often, cats. (Note that brachycephalic animals may do this due to nothing more than their abnormal conformation, however.) Other potentially serious reasons for this behavior include post-nasal drip (the dog is brewing a respiratory infection or has an active one), nasal polyps or tumors, nasal mites, or an actual obstruction like a blade of grass or foxtail. If the dog or cat begins to reverse-sneeze frequently or has prolonged bouts, a vet visit is immediately warranted, because the nasal passage may be obstructed. Also, dogs are less likely than cats and horses to have any respiratory signs of allergy, so a dog who coughs or appears to have breathing issues needs to see a veterinarian for a workup.

Coat abnormality: Coats may appear “moth-eaten” or stained due to excessive licking. Cats may have tracts of thinner fur (the practice is aptly called “fur mowing”) with an otherwise normal coat, and since the thinning happens in the course of grooming, many clients don’t associate it with pruritis (itching).

Pruritic face: Facial itchiness in dogs is fairly obvious. The dog might be rubbing their face by lifting a foreleg over and down on it, dragging their face along the carpet or other material, or pushing their face in between couch cushions or other materials and rolling it back and forth. Clients may interpret those signs as the dog rubbing their eye or trying to clean their face because they think itchy dogs use their back feet to scratch. Horses may drag their nose along the ground, and again this may look as if they are pushing dirt around rather than trying to scratch. For cats, see the cat subsection below.

Pruritic belly: The itchy underside is a classic in many species. Itchiness concentrated specifically around the base of the tail and groin, +/- some neck itchiness, is a marker for flea allergy. There is often saliva-staining. Cats with allergies will often overgroom the lower belly and inner thighs until the fur is sparse. While overgrooming can also be a sign of anxiety in the cat, a veterinarian should be consulted even if there is cause to believe the cat is anxious. An incessant itchy feeling does not help anxious cats either!

Ear discharge: Recurrent ear infections as well as excessively waxy upright ears can sometimes be the only signs of minor allergies. Animals do get a mild amount of wax buildup over time, as humans do, but it should be very slow; you shouldn’t find that it quickly reappears after you clean the ears. Note that dogs with conformational abnormalities such as excessively droopy or hair-filled ears have an intrinsic tendency toward infection.

Some unusual species-specific signs


Self-trauma to the neck and face. There is a typical pattern, and the trauma can be severe and spread to the entire face and neck. The client may not even notice excessive scratching until the cat has torn the skin. These cats easily develop secondary infections and may need antibiotics and a cone-shaped, plastic Elizabethan collar. (Soft collars won’t prevent the cat from rubbing their face on surfaces.)  If the lesions involve the neck, making a small turtleneck T-shirt can help keep the collar from irritating the torn skin. More typically, the cat will overgroom in the area of thinner fur between the eye and the ear and not cause enough damage for the client to think it’s pathological. It’s worth noting because it may be part of a larger allergy picture—let’s say the cat also vomits occasionally (a sign of food allergy)—that the client may not piece together.

Issues with the lips and chin. Cats can develop chin acne and lesions along their lips as a result of an allergic process. Clients may not notice smaller lesions. The reasons and differential diagnoses (for instance, rodent ulcers) are too extensive to detail, but again, lesions in this area may signal a larger health issue. As a side note, some cats seem to develop pustules on the chin when they are served food and water in plastic bowls. I always advise using glass, ceramic, or metal for all cats.

Vocalization and respiration. Airway signs can include a change in the voice (meow becomes softer, more coarse), a change in the purr (may seem louder, or grumbly or “wet”), or an outright cough. Often in the midst of purring or coughing you can see the cat swallow mucus that has traveled up the airway. Note that coughing in cats can often lead to vomiting, which makes the client think the cat has “hairballs” when really the cat could be coughing due to allergic asthma (or an infection like heartworm) and then vomiting as a consequence of the cough. Since cats groom frequently, in any given vomit you may find a clod of fur; it’s not a “hairball,” they’ve just vomited recently-groomed fur among other stomach contents.


Foot-licking. Reddish staining on the feet and between the toes is a sign of chronic foot-licking. Although this behavior can be anxiety-related, foot-licking (especially of the front feet) that occurs along with other signs is more likely to have an allergic component.

Excessive licking. There is a phenomenon of excessive surface-licking and air-licking; it isn’t common, but a study has firmly linked it to gastrointestinal issues. Among other causes, food allergy or intolerance (an adverse reaction to food that is not immune-related) is possible, and the licking should be considered as primarily a behavioral matter only once medical causes have been thoroughly investigated. This would be a perfect task for an internal medicine specialist, if available in the area. Since this kind of excessive licking often indicates a type of gastrointestinal distress (nausea, gastric reflux), it is a quality of life issue and should be addressed quickly.

Yeast dermatitis (aka “elephant skin”). This is marked by medium-sized to large lesions of dark skin such as these that may not even appear to be itchy. These are often signs of allergy. The skin may smell musty and may get crusty intermittently. These lesions are not the same as the calluses large dogs may form on their elbows.

Abnormal discharge. Allergic dogs can have excessive thick eye discharge without any obvious eye redness, inflammation, or irritation. Male dogs can have excessive preputial discharge (smegma) which is most visible when they first wake up (before grooming); the client may also observe them overgrooming the prepuce.

Next steps

For suspected allergic reactions, clients should consult their animal’s primary veterinarian. Food trials (cats and dogs), medication, flea treatment, and allergy testing may be ahead. To rule out flea and mite allergy, all itchy animals (indoor cats too) should go on a topical flea and mite preventive for three months (to cover them while flea eggs potentially hatch in the environment over time). Other medications include antihistamines, and possibly a course of steroids for animals with such severe itching that it interferes with quality of life. For food allergies, a food trial is the only real test and please don’t let anyone tell you different. You can spend money on blood tests if you like, but there is no true answer but a dietary trial.

Please note that a true food allergy trial must be done with prescription diets. “Limited ingredient” over-the-counter diets are less expensive but also more likely to have contamination that can render the test useless. With OTC foods, there is no guarantee that the food isn’t processed on equipment that has traces of other ingredients. Some clients may balk at the idea of using prescription foods, feeling that their current brand or recipe is better quality, but this is a test like any other medical test and should be done by the book. After the test period, other diets can absolutely be tried. Patients on a food allergy trial have to avoid all other foods, including flavored medications, for the duration of the trial (often four to eight weeks). This strict trial period is critical. Clients often struggle with this, and the behaviorist may help them by creating a management plan for the client; living in a household designed to discourage counter-surfing and trash-tipping and having a solid “leave it” can make the weeks go by much more easily.

For all other allergies, there are two main options: blood testing and skin testing. The point of allergen identification is twofold: to attempt to manage exposure to the allergen, and/or to undertake allergen immunotherapy (allergy shots). Most general practice veterinarians will do blood allergy testing but not skin tests; however, skin tests are more sensitive in all species and remain the gold standard. For horses especially, research has shown blood allergy testing to be inferior to skin testing.

In the veterinary world, dermatologists are the “allergy” doctors for itchy animals, doing the testing and formulating allergy shots, and internal medicine specialists most often manage cases of allergic bronchitis and asthma. Skin testing does require sedation (not full anesthesia) in almost all animals as they must lie still for more than 15 minutes while they receive injections into the skin. A client can do a blood allergy test and get a standardized allergy shot formula but if it doesn’t help, there is no way to tell whether the formula failed because a less sensitive (blood) test was used. If the client is considering giving allergy shots, the behaviorist can assist here by helping the client desensitize the animal to receiving the shots, as they are most easily given at home.

If you suspect a client’s companion animal has signs of allergy, take a moment to consider your approach before addressing the client. The majority of clients will be happy for your feedback, but some people can be particularly defensive if they sense an implication that they have left their animal in discomfort, or failed to notice something you demonstrably notice immediately. You may want to be slightly indirect; if you notice saliva-stained feet, for example, you can ask if they often see the dog licking his feet. I often take an approach that clearly establishes that what I’m referring to isn’t common knowledge: “[Species] can have some signs of allergies that you’d never expect, like [xyz]. They don’t get watery eyes and sneeze like we do; sometimes it just looks like they groom a lot. Have you ever noticed this with Fluffy?”

There may be a rare case where it seems clear that the issue is not behavioral at all, based on the signs. If the client tells you during your initial phone contact that the issue is self-mutilation of some kind, ask when their animal’s last veterinary exam was. If not recent, ask them to have that done first and if the vet does not find any medical reason, to please get a copy of the exam report and then contact you again. If there was a recent exam, and they say the veterinarian didn’t find a reason, agree to an appointment but also get a copy of the report. Clients misunderstand or sometimes outright ignore information they don’t want to hear, and a recommendation for expensive allergy testing and long food trials may fall into that category.

While an animal is undergoing treatment for medical consequences of allergic reactions, the behavior consultant can still play a key role. Whether it’s the allergy shots mentioned above, or wearing an Elizabethan collar, or having ear cleanings, or if a cat has to be medicated using the AeroKat, there is often a need for behavior modification to ease the way for both client and animal. (This holds true for so many medical treatments an animal may need, and is why I so heartily recommend that tolerance of gentle restraint should be part of “manners” training in every animal.)

The client, the animal, and the consultant all benefit when there is a strong relationship with a trusted veterinarian. Clients who aren’t happy with their veterinarian need to seek a new one; behavior modification programs can be less effective or even fail if good, thorough medical history and physical exam aren’t undertaken at the start. It’s worth seeking out good local general practice veterinarians and forming a relationship with them. The history you may be able to give the vet (that the client may not) can help them be as comprehensive as possible.


Jess has spent most of her career in veterinary technology working in critical care and cardiology. She has been published in the APDT’s Chronicle of the Dog and in the peer-reviewed journal Veterinary Technician, and is an accredited lecturer in her field.