Red Lines under armpit question?!
Question: Red Lines under armpit question?
Answers:
I am guessing that these Striations(medical Term) are a result of an intrinsic or extrensic nature.
Intrinsic: your boyfriend is working out a lot and may be developing stretchmarks; your BF is overweight and bacteria is infecting areas which are not cleaned well.
Extrensic: Possible environmental exposure (i.e. poison ivy); bedbugs (they bite in straight lines along blood vessels)
Give your BF 50 mg benadryl (2 benadryl) and apply some topical steroids (hydro-cortisone), you may try some neosporin as well.
It is very common thing. I'm no professional but I have seen many people with this "Rash" and nothing serious happens.