Tarmouth

Take it to a Vet.

However there are a few common snake ailments that can cause this,

1 If you have a basking lamp on its enclosure it may be too close and/or too hot.

2 It's developed a bacterial infection and needs a Vet to administer antibiotics.

3 Mites are a common problem that can cause skin irritation. Their eggs can lay dormant for years after the snake enters captivity. Bedding is usually an underlying factor that contributes to mite infestations. Can be easily cured by sterilizing the enclosure and several applications of vegetable oil.(no kidding it works)

4 Vitamin deficiencies can be known to cause skin irritation as well. However there is still alot of controversy over which vitamin causes this. There are many broad range, multivitamin, food suplements on the market that can help with this.


There's many more but those were the most common I found in the herpeculture scene.