Case study shows that cat bites can lead to allergies, and should be included in the medical history

September 14, 2022

2 minutes to read

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The main takeaway:

  • The girl had no history of cat allergy, atopic dermatitis or food allergy when she was bitten on the back of her hand and immediately developed two erythematous spots.
  • Two months later, the girl developed conjunctival redness, sneezing and breathing difficulties when visiting the house with the cat again.
  • Subsequent skin prick test was positive for cat dander, and specific IgE assays were positive for cat extract and rFel d 1.

A girl who was bitten by a cat and then developed an allergy to cats may be the first reported case of allergy through a cat bite, according to a letter published in Allergy and immunity in children.

Because the sting has disrupted the skin barrier, this condition indicates that the pre-existing barrier defect may not be a prerequisite for sensitization, Gualtiero Leo, MD, From the Pediatric Allergy and Asthma Unit, Department of Childhood and Developmental Medicine at ASST Fatebenefratelli Sacco Hospital in Milan, Italy, colleagues write.

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The girl, aged 7, was visiting a friend’s house in November 2021. The friend had a cat that bit the girl on the back of her hand. Although the girl had visited this house before, this was the first time the cat had bitten her.

Immediately, the girl developed a pair of erythematous spots without any bleeding. Two months later, when the girl visited this home again, she developed conjunctival redness, sneezing, and breathing difficulties within 30 to 60 minutes after arriving. A month later, she had another asthma attack in another house with a cat.

Allergy screening in March 2022 included a positive skin prick test for cat dander (8 mm) and IgE positive specific assays For cat extract (9.76 kU/L) and rFel d 1 (10.9 kU/L). Specific IgE assays for Fel d 2 and rFel d 4 were negative. The total IgE was 129.8 IU/mL.

Previously, at the age of 18 months, the girl began to suffer from frequent infections of the respiratory tract, accompanied by rhinitis, nasal mucous secretions and cough. She had no clinical history of atopic dermatitis or food allergy. A previous SPT test for inhaled allergens including cats, performed at 2 years and 10 months of age, was negative. She had no pets at home.

In September 2019, the girl started taking 50 micrograms of fluticasone once daily as a long-term treatment for asthma and to prevent exacerbation of upper respiratory infections. SPT in September 2021 tested positive for grasses (5 mm) and olive tree (5 mm), Dermatophagoid Meal (6 mm) and Dermatophagoides pteronissinus (6 mm), but negative for catnip extract.

Fel d 1, which the case study authors called The main allergen for catsIt is produced mainly by cat’s saliva and sebaceous glands. A cat bite can lead to anaphylaxis, according to the researchers, suggesting that the bite can contain enough allergens to trigger symptoms and sensitization.

The authors wrote that finding a new route to sensitizing cats to allergies is unlikely after decades of studies, although patient histories usually do not include information on cat bites. The authors, then, suggested that providers include specific questions about cat bites in medical histories.

Furthermore, the authors recommended future studies on the effects of tissue lacerations caused by cat bites, which could provide data on the high potential risk of cat dander sensitization due to cutaneous barrier defects.