Last week we launched our allergy series and provided an overview of what allergies can look like. As you will recall, symptoms might include itching, scratching, licking, chewing, ear infections, skin infections, sneezing, ocular symptoms, reverse sneezing, coughing, or vomiting and diarrhea (mostly seen with food sensitivities. This week, we are going to discuss how we examine and work up animals exhibiting these symptoms. The discussion today will be limited to skin and ocular/ respiratory allergy signs. We will devote a future blog to food allergies manifesting with gastrointestinal signs.
History:
First and foremost, when you provide historical information about the symptoms, you are helping us gain a deeper understanding of the situation. Here is some of the invaluable historical information you can share:
- When did the symptoms start?
- Has your pet experienced these symptoms before? If so, does it seem to happen the same time each year?
- Is your pet around other pets (where he/she could have come into contact with something contagious?)
- Does your pet go to the groomer?
- Is your pet on flea control?
- Where does your pet spend most of his/her time (indoors/outdoors)?
- Did you recently change something about your pet’s environment (e.g., new carpet, new shampoo, new laundry detergent)?
- What do you feed your pet? Did you recently change your pet’s diet?
- Is your pet taking any medications or supplements?
- If your pet has been treated for similar problems in the past, what treatments were effective?
Physical Exam:
Any animal experiencing symptoms consistent with allergies should have a physical exam performed by one of our doctors. It is especially important to note that prompt exam is critical for ocular and respiratory symptoms in order to rule out other urgent issues. By examining your pet from head to tail, our doctors are able to look for clues to better understand where the problem is coming from. Allergy symptoms can show up just about anywhere on the patient – eyes, ears, nose/respiratory tract, chin, neck, face, back, axillary region, abdomen, feet, lower back, under the tail, etc.). Sometimes the pattern of symptoms helps us understand the cause. The exam also allows us to assess how severely affected your pet is – which will ultimately guide our diagnostic and treatment recommendations.
Here are some of the more common physical exam findings we might see in a patient with allergies:
- Pruritus (the patient is itchy – exhibited through the patient licking/ chewing / scratching)
- Red, inflamed skin
- Hot spots
- Hair loss
- Greasy skin
- Dry, flaking skin
- Hyperpigmented skin
- Evidence of a bacterial or yeast skin infection
- Fleas or flea dirt
- Ear infections
- Malodor
- Ocular signs (red, itchy, watery eyes)
- Sneezing (with or without nasal discharge)
- Coughing
Considering Possible Causes of the Symptoms:
Once we identify particular symptoms and physical exam findings, we must also consider that these symptoms could be caused by something other than allergies. Here are some examples of the differential diagnoses we might be considering:
- Fleas
- Sarcoptic mange (zoonotic)
- Demodectic mange
- Ringworm (zoonotic; dogs and cats)
- Lice
- Dandruff / dry skin
- Bacterial or yeast infections
- Drug reactions
- Contact irritants
- Immune-mediated diseases
- Food allergies
- Environmental allergies
- If ocular involvement: corneal ulceration, ocular foreign body, glaucoma, uveitis
- If sneezing: Infectious diseases; foreign body in the nasal cavity; polyps (cats)
- If coughing: Inhalant irritant; Infectious diseases; cardiac disease; lung disease; collapsing trachea
Performing Diagnostics:
There are several skin diagnostic tests that can be performed easily and rapidly in the clinic. Skin cytology samples can be examined under the microscope to better understand the cell populations involved and to look for evidence of bacterial or yeast infections. Skin scrapings can also be examined microscopically to look for mites. Fungal cultures can tell us whether ringworm is the cause. Fleas and possibly lice can be visualized by looking closely at the skin and hair coat. Occasionally, lab work may be recommended to look for metabolic, endocrine, or immune-mediated explanations for the skin condition. Allergy testing and skin biopsies are also sometimes recommended.
In addition to a thorough ocular exam, testing for ocular symptoms might include staining the cornea to look for ulceration, or checking the ocular pressures. When trying to understand the cause of lung disease, our doctors will first observe how your pet is breathing, and then carefully listen to the lungs and heart. Radiographs may also be used to help elucidate potential causes of sneezing or coughing.
We don’t necessarily perform every diagnostic test on every patient. The extent of diagnostic testing is determined by things such as symptoms, severity, and index of suspicion for a particular problem. Many of the tests can be performed sequentially – so if we get a positive result on something, we might stop there and treat the identified problem before continuing with additional diagnostics. As if allergies were not complicated enough, we often see a pet with primary allergies come in with secondary skin and ear infections. The itching, irritation and inflammation that develops in allergic patients creates a local environment that can allow for an overgrowth of bacteria and/or yeast. So, if we find evidence of infection, we may consider treating for the infection as well as allergies at the same time.
What’s Next?
As you have seen above, working up allergies is not always straight forward. It’s so important to rule out other possible causes of symptoms before settling on a diagnosis of allergies. But we also have to address the patient’s comfort as quickly and effectively as possible – sometimes even before we have our final allergy diagnosis. Next week we will talk about the different management strategies that are available for the allergic patient – so stay tuned!
Author: Dr. C. Noureddine, DVM, MS