Spicy foods:
The chemicals present in spicy foods typically causes irritation of the tongue mucosa where it detected as being ‘hot’. This effect persists as it travels through the gut. If these irritants are not degraded or neutralized by the time it reaches the rectum, it will cause local irritation of the anal mucosa. The inflammatory response also causes redness and sometimes swelling of the affected area. The most common irritant foods is capsicin present in chilli and peppers but a host of other chemicals in foods can have a similar reaction. The burning sensation usually starts after a bowel movement and persists for a period of time afterwards. Spicy foods may also cause mild diarrhea which can irritate the anus and lead to burning.
Tongue mucosa? Anal mucosa? Seems like ass to mouth porn was trailblazing afterall.