You can be certain that a rash on the arm is not due to HSV-2 and almost certainly not HSV-1. "Painful blister clusters" is a great description of herpes, however, and herpes zoster (shingles) sounds like a possibility. Although most common in older people, shingles is not rare in younger, sexually active persons (my son had it at age 13).
Shingles is a recurrence of childhood chickenpox in localized form. It does not travel to other parts of the body. It cannot be transmitted to people who had chickenpox as children or who have been vaccinated against chickenpox--which includes almost everybody. So if that's what your partner has, you have no worries about catching it in your genital area or anywhere else.
Your partner should see a health care provider immediately to see if he has herpes zoster. If so, his provider might prescribe an anti-herpes drug like valacyclovir or famciclovir. Some cases of shingles are followed by severe pain due to post-herpetic neuralgia, which can continue for months or years; the risk is reduced by treatment, but only if it is started early. So don't delay.
But don't worry about genital infection or transmission to you. Good luck--
HHH, MD
I cought the papillon and genital herpes viruses from my ex boy friend who was awfully active and had sex with as many girls as he could and finally he gave me those two awful things before I leave him but any ways, my doctor told me I have no genital herpes and even tough I see it some times on me. I get some times one little out break small one on my arm or upper leg area and right away i put little alchool and cover it with a cotton and leave it like that till it dries out. I am really afraid that it enters inside my eyes or my son catchs it from me. I have a three years old boy whom I notice he gets some times the little pimples inside his nose adn it seems very itchy but hope fully that would not be transfered to his penis. I wash my personal stuff but it is some times impossible to tell him not to touch my personal stuff because he is still a baby! I wash my hands with alchoola dn I know using and rubbing a bit of alchool destroys the out break faster. I also have asthma, adn that can complicate my asthma adn respiratory area as well.
It could be shingles. I would doubt it's genital herpes on his arm.