My boy develops a redness on the inside of his thighs on either side of the genital area. The odd thing is that it comes and goes. The vet noticed it and said he had sensitive skin and gave me a topical spray to use for a week. But it comes back. I've noticed that it seems most "irritated" after he comes in the house and especially after running around in the yard. We have had an unusually snowless winter this year and I'm wondering if he could be irritated by the straw, dead plants, dust that he kicks up. I've also noticed that dirt accumulates espeicially in the skin folds by the testicles so could this maybe be what's causing the irriation in the general area?

That is what I was thinking. We have some tall grass and rosebushes, etc that aren't covered by the snow this year. I have not noticed much redness but sometimes he does come in with a couple rose thorns in his thighs and those areas turn red.

Spencer gets that on his thighs sometimes in the summer. I thought it was a heat rash, but maybe he's been around prickly stuff in the yard. I rub a little lotion on it, and he seems to think that's the equivalent of a doggy massage. I watch him to make sure he doesn't lick it off, and the red is usually gone in a day.