When I was a boy I occasionally got raised itchy bumps on my skin that disappeared after a while. Many years older now, I get them again. What causes them?

small bumps, many of them together?

 

If small, and multiple, could be heat rash.

 

Heat and humidity cause it.

5 minutes ago, Sheryl said:

small bumps, many of them together?

 

If small, and multiple, could be heat rash.

 

Heat and humidity cause it.

It's not heat rash, Sheryl. But thanks for your reply. 

7 minutes ago, Gandtee said:

It's not heat rash, Sheryl. But thanks for your reply. 

Then if it is also not an oisect bite, and it persists, best to see a dermatologist.