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Then you aren't taking the right amount or right specific antihistimine. There are at least a dozen different antihistimine medications, because so many people react better to certain ones, may not respond well to some of the side effects (ie benadryl makes you drowsy but loratidine doesn't, although it is weaker). You can also easily gain a tolerance to them.
Benadryl // Diphenhydramine HCl is the most effective for most people. If that doesn't work, there are many others you can try out - chloriphinean maleate [sic], loratidine, dimenhydrinate hcl, one that just recently got turned from prescription to OTC ....
The itches are caused by a massive release of histimines in your body when you take dope, the same stuff released by being around allergens. Taking an anti-histimine will counteract this.
Nose gets itchiest because a lot of histimines are released there. This is natural since usually, allergens are inhaled through the nose. Evolutionary, intelligently designed, whatever, that's where a lot of histimines go to by the simple design of your body.
This question could easily be answered by a search engine man. Please use the search function before posting a new thread, 99.99% chance your question has already been asked and answered. It's a much faster way to get an answer, and the same old threads over and over get old quick. If you have further questions just bump an old thread instead of making a new one.
Welcome to Bluelight. Use The Fucking Search Engine (UTFSE)