Dermatology Questions? Ask an Online Dermatologist.
This is Dr. David
a slight line blister rash which is sore can be a sign of shingles rash on the skin
how old is your boyfriend?
can you upload a clear jpg photo of the rash here online so I can see it?
that could be dermatitis from irritation or allergy.
that looks like it is at his waist line
new pants or a new belt could be irritating his skin there at that line.
new detergent washing his clothes or bet bathing suit on that area for too long can cause a line irritation like that at his waist line.