Mosquito Bite Hypersensitivity in Cats

Mosquito bite hypersensitivity in cats is an exaggerated immune response to proteins in mosquito saliva. When a mosquito feeds, it injects saliva containing anticoagulants and other substances; in susceptible cats, the immune system responds more intensely than typical, leading to persistent inflammation at bite sites. The condition is most commonly seen in areas where mosquitoes are active, and tends to affect outdoor cats or those in homes with access to gardens during warmer months. Owners typically notice crusted, scabby lesions on areas with less fur—particularly the nose, ears, and paw pads—that may appear after mosquito exposure. The affected skin can look red, swollen, or ulcerated, and the lesions may be itchy or uncomfortable. Because the distribution often follows a pattern (exposed, thinly furred areas), the appearance can raise questions about what might be causing these recurring changes. This page explores what mosquito bite hypersensitivity can look like in practice, the immune mechanisms that drive the reaction, how the condition is distinguished from other causes of facial and ear lesions, and the range of approaches used to manage symptoms and reduce exposure. The focus throughout is on understanding what may be happening and what options exist, rather than diagnosing any individual cat.