What is a cat scratch allergy?
A cat scratch allergy is an allergic reaction to proteins found in cat saliva, skin, or fur that triggers an immune response when a person is scratched, bitten, or licked by a cat (1). It is caused by an overreaction of the immune system to these foreign proteins. Symptoms appear within minutes to hours after exposure and can include redness, swelling, itchiness, and hives at the site of the scratch or bite.
Who gets cat scratch allergies?
Cat scratch allergies are more common in adults than children. According to a review, around 10-20% of adults worldwide are allergic to cats, and this percentage has been increasing over time (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8721548/). People with a pre-existing allergy to cats are more likely to develop cat scratch allergies. Additionally, people with weakened immune systems may be more susceptible to allergic reactions from cat scratches.
Symptoms
The most common symptoms of an allergic reaction to a cat scratch are localized redness, swelling, and itching at the site of the scratch. This reaction can develop within minutes to hours after being scratched and may last for a few hours to several days (https://www.hopkinsmedicine.org/health/conditions-and-diseases/cat-scratch-disease).
The redness and swelling often spread beyond the initial scratch line. A red streak may extend from the wound as the skin reaction spreads. The surrounding skin can become hot, firm, and very itchy. The scratch line and surrounding swelling may be slightly painful or tender. This reaction indicates the body’s immune response to proteins found in cat saliva that were introduced during the scratch (https://my.clevelandclinic.org/health/diseases/23537-cat-scratch-fever).
Some people may also experience swollen lymph nodes near the scratch or hives. Severe itching of the skin around the scratch is common. Scratching can worsen the skin reaction. Topical steroid creams and oral antihistamines may help relieve itching and inflammation (https://www.emedicinehealth.com/cat_scratch_disease/article_em.htm).
Diagnosis
Diagnosing a cat scratch allergy begins with getting a detailed patient history. The doctor will ask about any recent scratches or bites from a cat, symptoms that developed afterwards, and the timeline of those symptoms. They will also inquire about potential exposure to fleas or ticks that the cat may have been carrying.
Allergy testing may be done to confirm an allergy to proteins found in cat saliva. This can involve a skin prick test, where possible allergens are pricked into the skin to observe the reaction. Blood tests can also detect IgE antibodies produced when someone is allergic to a substance.
The doctor will thoroughly examine any cat scratches or bites. They will look for signs of infection, redness, swelling, pus, and enlarged lymph nodes near the area. Taking a sample of fluid from an infected scratch can allow testing for bacterial organisms.
Treatment
Treatment for allergic reactions to cat scratches focuses on relieving symptoms and preventing infection. Antihistamines like diphenhydramine (Benadryl) can help reduce itching, swelling, and other allergy symptoms [Cleveland Clinic]. Topical steroid creams may also provide relief when applied directly to the affected area [Family Doctor].
Cool compresses can soothe skin irritation and itchiness. Gently applying a cool, wet cloth to the scratch for 10-15 minutes several times a day may provide relief. Over-the-counter pain relievers like acetaminophen or ibuprofen can reduce pain and discomfort [Johns Hopkins Medicine].
For severe allergic reactions, oral corticosteroids like prednisone may be prescribed to reduce inflammation and suppress the immune response. However, steroids have significant side effects with prolonged use, so they are generally reserved for short-term treatment in acute cases [Cleveland Clinic].
Prevention
There are several ways to help prevent allergic reactions to cat scratches:
Keep cats’ claws trimmed – By keeping cats’ claws short and dull, their scratches are less likely to break the skin and cause an allergic reaction (source).
Wash hands after petting – Washing hands with soap and water after petting or handling cats can remove allergens and prevent symptoms (source).
Cat allergy shots – Allergy shots containing small amounts of cat allergens, given over time, can help build tolerance and reduce allergic reactions to scratches (source).
Avoid rough play – Playing gently with cats, and not encouraging scratching/biting during playtime, can help prevent skin contact with saliva or scratches that trigger allergies.
Prognosis
For most people, the symptoms of a cat scratch allergy usually resolve within a week or two (CDC). The rash and fever tend to clear up first, while lymph node swelling may persist for a bit longer. With proper treatment and care, the prognosis is generally good.
However, in some cases, the allergy can be chronic and last for several weeks or months (Baranowski et al.). This is more likely if the infection spreads to other areas of the body. Young children and those with weakened immune systems may also have prolonged symptoms. In these instances, close follow up with a doctor is recommended to monitor recovery and watch for complications.
While extremely rare, cat scratch allergies can potentially be fatal if they affect vital organs like the brain, heart or liver. However, most people make a full recovery within several months at most.
Complications
While most cases of cat scratch allergy are relatively mild, there can be some potentially serious complications to be aware of, including:
Skin infection – The scratch or bite wound can develop a bacterial infection, which will result in increased redness, pain, swelling, oozing of pus, and fever. This requires prompt medical treatment with antibiotics.
Long-lasting rash – In some people, the rash from a cat scratch allergy can persist for several weeks or months. Though not dangerous, this can be uncomfortable and annoying.
Breathing issues – Rarely, the infection from a cat scratch can spread from the initial site and affect other areas of the body. If it spreads to the lungs, this can cause pneumonia with coughing, difficulty breathing, and low oxygen levels. This is a medical emergency requiring hospitalization.
When to see a doctor
You should see a doctor if the rash from a cat scratch allergy spreads or worsens, you have breathing difficulties, or develop a fever or pus from the scratch. According to the experts at Cleveland Clinic, you should seek medical care if the rash spreads beyond the site of the scratch or if you develop swelling in the lymph nodes in your armpit or groin.
Cat scratch disease can lead to more serious complications in some cases, so it’s important to monitor your symptoms closely. As Hopkins Medicine explains, call your doctor if the rash worsens or spreads even after a few days, if you develop a fever over 102°F, have difficulty breathing, or notice pus draining from the scratch.
Getting prompt medical attention is advised if symptoms are worsening or spreading. Your doctor can determine if antibiotics are needed to treat the infection and prevent potentially dangerous complications.
Coping with cat allergies
There are several ways to cope with cat allergies if you want to live with cats:
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Take allergy medication like antihistamines or nasal corticosteroid sprays to reduce symptoms (1). These won’t cure the allergy but can provide relief from sneezing, itchy eyes, and a runny nose.
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Use high efficiency particulate air (HEPA) filters in your home to remove allergens from the air (2). Place air purifiers with HEPA filters in rooms where you spend the most time.
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Keep cats out of your bedroom since that is where you likely spend the most time (3). Making your bedroom a cat-free zone reduces exposure to allergens.
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Clean frequently to remove cat dander and hair from surfaces. Use a vacuum cleaner with a HEPA filter and wash bedding weekly in hot water (3).
While cat allergies can’t be cured, managing symptoms and reducing exposure can make living with cats more bearable.
Sources:
(1) https://www.petfinder.com/cats-and-kittens/health-wellness/concerns/tips-for-living-with-cat-allergies/
(2) https://vet.osu.edu/sites/vet.osu.edu/files/legacy/documents/pdf/education/mph-vph/allergic%20to%20your%20cat.pdf
(3) https://www.cats.org.uk/oxford/feature-pages/living-with-cat-allergies