Why is my cat running in circles with crusty bumps on her tail?

Hello, and thank you for your question. The bumps on the tail could be related to parasites such as fleas, or a bacterial or fungal infection, or a skin allergy. Her behaviour of running around is likely due to itchiness.

I would recommend a vet visit within the next few days. They can examine the skin for parasites, and potentially perform tests such as a skin scraping or fungal culture. If a bacterial infection is suspected, they can prescribe antibiotics. At minimum, anti-itch medication can be prescribed while they figure out the underlying cause.

For now, you can try bathing the affected area with a gentle aloe and oatmeal shampoo. Rinse well with lukewarm water and pat dry. I'd also advise putting an e-collar (cone) on her head to prevent her from further licking or biting the skin and making it worse.

I hope this helps, and that Bling feels better soon!