It’s always with you if you have it, sadly. Many other thing can cause similar issues.Ooof - my brother had stuff exactly like that in blotches all up both legs as a kid - they thought it was meningitis related at the time and pumped him full of all kinds of stuff - never got to the bottom of it but he recovered and is still here 30 years later fine.
EDIT: He also developed an asthma like condition before it. Sounds like he had a brush with Churg Strauss syndrome.
Possible he had a close escape.