Scab

It means a scab: the crust over a healing sore.

The Eastern Han Chinese dictionary Shuowen Jiezi glosses 痂 as scabies, a skin disease. In the character, 疒 marks illness and 加 supplies the sound.

Chinese compounds show the healing-wound sense: 结痂 describes a scab forming, while 痂皮 names the crust itself.

is 痂 used in Japanese

Yes: Japanese can use 痂 for an everyday scab.

Japanese can use 痂 to write the everyday word かさぶた; 痂皮 is a technical term for the crust, read かひ.

Traditional Korean medical sources record 痂 in compounds such as 痂皮 and 結痂, where it is read 가. The written character is shared, but these are language-specific readings and terms.

why did someone send 痂

Read it literally as a scab; the sentence sets the tone.

Alone, 痂 names a scab or crust; the surrounding sentence decides whether it is a plain medical reference or a joke.

The Chinese idiom 嗜痂成癖 describes an extreme liking for scabs. A Southern Dynasty anecdote tells of a man who supposedly enjoyed eating them; the idiom is literary and grotesque, while 痂 alone does not carry that punch.