Dear Dr. Eva,

I have an itchy rash under my testicles and on my inner thighs. I’ve been told it’s jock itch. I’ve used different creams, but it keeps coming back. Could this be a sign of something serious?


Dear T.J.,

Probably not. Jock itch (the medical name is tinea cruris), which is caused by a fungus, is often hard to get rid of. You need to keep the area as clean and dry as possible, apply antifungal cream or powder twice a day every day, and keep applying it for a couple of weeks after the rash seems to be gone. Fungus grows slowly and takes a long time to get rid of. If it doesn’t go away after six weeks, consider getting checked for diabetes, which could make you particularly susceptible to fungus infections.

Dear Dr. Eva,

I recently noticed a round red sore on my scrotum, about 1/4-inch across and bowl-shaped. It didn’t hurt, and it went away on its own. Do I need to get checked by a doctor?


Dear Concerned,

Yes, please see your doctor or go to an STI (sexually transmitted infection) clinic. Most city Health Departments have an STI clinic, free or low cost.

There are several things this sore could be. The most serious cause is syphilis. Ulcers caused by syphilis are usually painless and single (meaning there is only one sore at a time found on the person – nothing to do with relationship status!). Syphilis ulcers do go away on their own, but that does not mean the syphilis infection is gone. The body cannot recover from syphilis without antibiotics. It becomes an internal disease, eventually damaging the spinal cord, brain, bones and other organs. Please see your doctor, or go to an STI clinic, and ask for a blood test for syphilis. (Also see the letter below for a related question.)

Dear Dr. Eva,

I recently developed a red rash all over. When I went to my doctor, she had me take a blood test for syphilis! I told her I haven’t had any sores or discharge – why does she think I would have syphilis? I thought it caused sores on the genitals, not a rash all over. Of course, the test came out negative. Do I need a different doctor?


Dear Skeptical,

Stay with your doctor – she’s doing the right thing. You’re right: the first stage of syphilis is a skin ulcer – but if the ulcer appears inside the vagina or rectum, or in the throat, you may never notice it. The second stage, called secondary syphilis, is a rash, which (unlike most rashes) often covers the palms and soles of the feet as well as the arms, legs, and trunk. In most cases it doesn’t itch. There’s a lot of variability in how the rash looks, and it is often mistaken for other skin conditions. So it’s always reasonable to test for syphilis if you have a widespread rash, unless a different cause is known for certain. The dangerous thing about the syphilis rash is that, if the person isn’t treated, the rash will go away on its own, but the disease continues to spread internally.

Dear Dr. Eva,

What is ringworm? Is it really a worm?


Dear R.T., Like a lot of medical conditions, ringworm (the medical name is tinea corporis) has an inaccurate name that reflects outdated, mistaken ideas of what causes it. Ringworm is caused by a skin fungus. The name comes from the circular pattern of the rash, which looks like a raised red circle with normal-looking skin inside the circle. It is contagious, especially in children. It can be treated with antifungal creams, but the cream must be used daily for a month, even if the rash has cleared up, to keep it from coming back

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Dr. Eva Hersh, MD
Dr. Eva Hersh, MD
Eva Hersh is a family physician. Send your comments and questions to her by email at