Why a 4 kg cat's single lick isn't a crisis
Your cat's small exposure means she likely didn't ingest enough avidin to cause immediate harm. The protein that interferes with biotin absorption needs consistent, repeated intake to create deficiency issues. For perspective, a cat would need to eat multiple raw egg whites weekly over several weeks before showing symptoms. The trace amount from licking a surface poses minimal risk to her coat or skin health.
That said, her size does make her more vulnerable than larger animals to cumulative effects. If she starts compulsively licking her paws, develops flaky skin patches, or shows unusual hair thinning in the next month, those warrant a vet visit. Cats hide discomfort well, so watch for increased scratching or changes in grooming habits too.
Cooking changes everything for feline safety
Heat permanently alters avidin's structure, rendering it harmless. Scrambled eggs (plain, without additives) or hard-boiled yolks become safe protein sources because cooking neutralizes the risk. The butter in your question adds unnecessary fat that could upset her stomach—stick to unseasoned preparations. Even the yolk's high cholesterol matters less for cats than dogs since felines process animal fats more efficiently.
Transitioning to cooked eggs eliminates the guessing game about amounts. You can offer a teaspoon of cooled scrambled egg as an occasional treat without tracking cumulative exposure. Just ensure it's fully set—runny whites may still contain active avidin. Her 4 kg body will utilize the cooked protein far better than raw.
When yolk becomes the safer choice
Egg yolks contain biotin naturally, which counteracts any minor avidin exposure from contaminated whites. For cats prone to hairballs or with pre-existing skin conditions, the yolk's biotin content provides extra insurance. The fat-soluble vitamins (A, D, E) in yolks also support skin and coat health better than whites alone. Your cat's small size means even a quarter teaspoon of cooked yolk delivers noticeable nutritional benefits.
Monitor her stool after introducing yolk—some cats develop looser bowels from the richness. If she tolerates it well, the yolk's choline content may aid her cognitive function too. This makes cooked yolk doubly advantageous: it bypasses the raw white risk while delivering compounds that actively protect against deficiency symptoms.
The timeline for spotting problems
Biotin deficiency manifests slowly—if this single lick caused any issue (unlikely), you'd notice subtle changes around week three. Early signs include dandruff-like flakes along her spine or a coarser texture when stroking her fur. Cats often show fatigue through increased napping or reluctance to jump onto favorite perches. These develop gradually, giving you ample time to intervene.
Compare her current coat quality by parting fur along her back—take a photo today for later reference. Healthy cats should show smooth skin without redness. Since she's only 4 kg, her smaller body reserves mean symptoms might appear slightly sooner than in larger cats, but again, one lick rarely triggers this. Cooked eggs prevent this worry entirely.
The step-by-step response, from the first minute to the vet visit, is in our Raw Egg Whites (Avidin) Poisoning emergency guide.