You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

The veterinary literature contains references to skin lesions caused by drugs, but in practice few clinicians seem to have seen a case.

Veterinary textbooks on dermatology describe a variety of toxic reactions to drugs causing skin lesions that vary from mild erythema or urticaria  to necrolysis. In some cases systemic signs are seen as well. Penicillins, cephalosporins and sulphonamide antibiotics are most frequently implicated but that may simply reflect their wide usage in veterinary practice. 

The initial diagnosis is usually based upon known exposure to the drug prior to the onset of the signs and resolution of the signs when the drug is withdrawn. Confirmation of the diagnosis can only be made if the animal is subsequently provocatively challenged with the drug, but this could be risky if the initial "reaction" was immune-based because the animal could develop a life-threatening anaphylactic reaction following re-exposure.

Drugs Reported to Cause Skin Reactions in Cats and Dogs

Any drug can cause a reaction. Pruritus is a common finding irrespective of the route of administration, and the following specific manifestations of skin disease have also been reported* :

 

Drug	Skin Reaction(s) Reported
Antibiotics in general	Angioedema, Urticaria,
Amitraz	Angioedema, Urticaria
Ampicillin	Pemphigus
Antisera	Angioedema, Urticaria
Aurothioglucose	Erythema multiforme, Fixed drug eruption,
Azathiaprine	Alopecia, Secondary infection
Bacterins	Angioedema, Urticaria
Barbiturates	Angioedema, Urticaria
Bleomycin	Ulceration over pressure points. Loss of claws.
Blood transfusion	Angioedema, Urticaria
Cephalosporins	Angioedema, Urticaria, Erythema multiforme
Chlorambucil	Alopecia, Secondary infection
Chloramphenicol	Erythema multiforme
Cimetidine	Pemphigus
Cyclophosphamide	Alopecia, Secondary infection
Cyclosporine	Hirsuitism, Lymphoplasmacytoid dermatosis, Papillomatosis
Diethylcarbamazine	Erythema multiforme, Fixed drug eruption, Pemphigus
Diphenhydantoin	Atrophy, Increased fragility
Doxorubicin	Alopecia, Flushing, Pruritus, Secondary infection
Etoposide	Angioedema, Urticaria
5-fluorocytosine	Fixed drug eruption
Gentamicin	Angioedema, Urticaria, Erythema multiforme
Glucocorticoids	Post-injection atrophy, Alopecia, Secondary infection
Hydroxyurea	Alopecia, Secondary infection
Ivermectin	Angioedema, Urticaria
Ketoconazole	Epitheliotrophic lymphoma
Levamisole	Alopecia (patchy), Angioedema, Erythema multiforme, Exfoliative erythroderma, Pustules, Urticaria,
Lincomycin	Exfoliative erythroderma
Mechlorethamine	Alopecia, Secondary infection
Penicillins	Angioedema, Urticaria, Erythema Multiforme, Vasculitis
Primidone	Lupus erythematosus
Procainamide	Pemphigus
Progestagens	Post-injection atrophy
Propylthiouracil	Angioedema, Urticaria
Radiographic contrast media	Angioedema, Urticaria
Retinoids	Mucocutaneous erythema and crusts
Shampoos (insecticidal usually)	Superficial suppurative necrolytic dermatitis in Schnauzers (Miniature)
Sulphonamides	Alopecia (patchy), Angioedema, Urticaria, Erythema multiforme, Exfoliative erythroderma, Pemphigus, Pustules, Vasculitis
Tetracycline	Angioedema, Urticaria, Erythema multiforme
Thiabendazole	Pemphigus
Thiacetarsamide	Fixed drug eruption,
L-Thyroxine	Erythema multiforme
Triamcinolone	Bullous pemphgoid
Vaccinations	Angioedema, Lupus erythematosus, Post-vaccination panniculitis (eg rabies), Sarcoma formation (eg post-rabies vaccination in cats) Vasculitis (eg rabies), Urticaria

*Table modified after Scott et al. Small Animal Dermatology 5th Edition (available through Provet's On-line discount Bookshop CLICK HERE)

Provet Feedback Request

In humans cutaneous drug reactions may occur in as many as 3/1000 courses of drug therapy. Are we missing the diagnosis in our veterinary patients ? If you have seen a confirmed case of drug eruption please send Provet the details and we shall collate all reports. If we acquire enough data we shall publish the findings later.

Thank YOU

Updated January 2016