Greetings. Welcome to the HIV prevention forum. Your style and vocabulary suggests you are a health professional and I will respond accordingly.
I'm not an expert in exercise-induced or cold-induced urticaria -- which I believe are essentially the same thing -- but that strikes me as a likely possibility here. (I know about mostly from personal experience; my dad had it.) In any case, the rash of ARS is not pruritic or, to my knowledge, urticarial, and it never or almost never is the only manifestation. Fever and sore throat normally are present, and lymphadenopathy certainly is very common -- their absence, especially fever, is strong evidence against acute HIV infection. And I believe hydrocortisone would not affect the rash of ARS, although I have no direct knowledge about it.
As for a "candida like" oral problem, it's conceivable that's related to your recent antibioitics (which ones?) for your LRTI. But more likely it isn't candida at all; coated tongue and related anomalies are common in most garden variety URIs and other respiratory infections. And even if candida, it can happen de novo in healthy persons (I had it myself once). Finallly, oral candidiasis is a primarily manifestation advanced HIV infection, not ARS.
On top of all this, it sounds like your exposure was entirely protected. Oral sex carries such low risk of HIV transmission that some experts believe it to be zero. Combining the odds for this low risk exposure plus symptoms that really don't match up well with ARS make it extremely unlikely you caught HIV. But of course if you remain concerned, have an HIV antibody test in a few weeks. In the meantime, you should see see your personal physician or a dermatologist promptly. As you likely know, learning the true casue of your rash will be a lot easier the sooner it is evaluated.
A final comment: you don't mention your partner's HIV status, and it would be good to know he said he is HIV negative. Of course that's not perfect, since people can lie (but most don't) or might have been infected since last tested. Still, in the long run, knowing and exchanging HIV status before sex -- and avoiding exposure or at least being especially compulsive about condoms for anal intercourse -- is just as important a safe sex strategy for MSM as condoms for anal sex.
I hope this helps. Best wishes-- HHH, MD
Thank you for your answer and you guest correct- i am a fellow health care provider. The ab's were co-amoxiclav. I went to my GP to day advised and she thinks it's a folliculitis which she put me on flucloxacillin for.
Thanks your professionalism.
Kind regards