Hello, thank you for using Petco Pet Education Center, formerly Petcoach. Poor Molly, that looks uncomfortable. Molly may be having some type of allergic reaction that has become infected. Make sure you are using a good flea product, not just a cheap one from WalMart. If Molly will let you, you can try bathing her in a medicated shampoo that has Benzoyl Peroxide. If not, please have her seen by your veterinarian. She may need to be treated with a steroid injection &/or antibiotics to clear this up, or to get to the source of the irritation. Take care.