This happened to me about five weeks ago ,although I had been going to the clinic for two weeks before this happened.
I had come out in a rash all over my upper half, arms and legs, and went to the doctor. He examined me and said it was an alergy and arranged for me to attend a clinic for treatment.
When I went, a male nurse in his late twenties attended to me. He told me to strip down to my underwear which I did. He slipped my underpants down a little and started to give me my treatment which was using a paste that he brushed on. He, then, rubbed it all over the affected areas, but each time he rubbed the inside of my thighs, he nudged my balls and I soon started to get hard. Once the paste dried, I got dressed and left till next time.
The third time I went, he again said to strip. I did as usual except this time, he said to remove my underpants as well so he could check that I had no rash in that area.
So there I was, totally naked as he applied the paste. He now put some on my buttocks and some just above my cock. He said, 'Better safe than sorry,' and started rubbing it in as usual.
He then rubbed my buttocks and slipped his hand between my thighs and nudged my balls. Then he told me to face him and he started rubbing around my pubic area, then my balls and finally, he started rubbing it over my cock which was already getting hard.
He rubbed his hand up and down my shaft and soon I could hold on no longer and spurted cum over the floor. He said not to worry and while the paste dried he would wipe the floor. I noticed the front of his trousers and you could not miss the bulge of his cock.
This has now happened again since this event, and I am glad to say I go back tomorrow for more treatment. I don't know how long I will have to attend, but who cares, I am having fun.