which form of anthrax involves a black eschar on the skin?
Symptoms of cutaneous anthrax start 1 to 7 days after exposure: 1  An itchy sore develops that is similar to an insect bite. This sore may blister and form a black ulcer (sore or eschar). 2  The sore is usually painless, but it is often surrounded by swelling.  A scab often forms, and then dries and falls off within 2 weeks.