If it gets bigger, potentially hasten going to the vet. Can you take a wet Q-tip and kind of rub the area to get a better view of it? The white could be a lot of caked-on flakes. Your description reminds me of what Wick gets occasionally as his fur grows back after shedding from his current ringworm infection.

It doesn’t look too bad. You could try and scrape it with a q tip or broad end of a plastic tooth pick, to check if it’s caked up skin flakes, in which case it could be fur mites. It’s not in a typical location though and it looks very minor. Keep an eye on it. If it gets bigger, if you see loose dandruff, if she starts itching it, you see sepage, or a crust forming – in short, if it starts to look like sth is going in the wrong direction, you should book her a vet appointment.

It might be that she’s scraped off a bit of fur on the cage grids and it’s now growing back.

She’s extremely cute =)

Mites can come in on hay. But buns can also carry mites with them from when they were babies. The mites exist in low numbers and don’t make any trouble, the bun’s own immune defense keep them in check. Then something happens that challenges the bun’s immune defense, and the mites seize the opportunity to start multiplying. You get symptoms like white crusts, dandruff-like flakes and sometimes, but not always, the bun starts scratching itself.

The best treatment is Revolution (selamectin) or ivermectin. Both meds are prescription only unless you’re in Australia. They are highly effective and bunny safe.

And now the warning we always give whenever someone mentions mites or other skin parasites: Never use any compound containing Fipronil on buns. It’s deadly toxic to them. Many different fipronil-containing preparations are sold OTC for dogs and cats, so they’re readily available. They’re safe for dogs and cats, but must never be used on rabbits.