Skin rash

Very possible.

Radiation dermatitis is a side effect of external beam ionizing radiation. It is also called radiodermatitis, x-ray dermatitis, radiation skin damage or a radiation burn. Most commonly, radiation-induced dermatitis is caused by radiotherapy for underlying malignancies. Radiation dermatitis is one of the most common side effects of radiotherapy for cancer, affecting approximately 95 percent of patients receiving radiotherapy, and 87% will experience moderate to severe radiodermatitis during or after their therapy.

I would let the radiation oncologist know and they can give you to help relieve the symptoms and prompt healing.

It's not at all likely from the radiation.

Skin reactions to prostate radiation are almost unknown with modern IMRT machines. Because the prostate is deep inside, they use megavoltage X-rays that penetrate deeply and deposit little energy at the surface. In some very sensitive individuals, there may be an immediate reaction, but unlikely this long after treatment. The reaction on your neck is another clue that it could not be from radiation - radiation was nowhere near there.

I'm just guessing, but it sounds like this dermatitis is occurring where your underwear is in contact with your skin - the waistband, penis, crotch, and the neck of your T-shirt. It may be contact dermatitis. Did you use a new kind of detergent?

- Allen

I had a similar reaction. Saw a dermatologist who gave me a gel to apply and it was gone in a few days. Scary!
Bob