This is a very common, embarrassing, condition especially in men and presents with a very uncomfortable itchy anus. Often no obvious cause can be found.  Examination reveals red, inflamed, thickened skin in the genital area around the anus. It is difficult to treat, with frequent relapses. 

It can be caused by skin diseases around the anus including, psoriasis, eczema, lichen planus.  Candida (thrush) or fungal infections  can also cause an itchy bottom but this should be apparent on examination.  

Threadworms can cause itchy bottoms in children and is common.  It is not as common in adult patients. Your Doctor may suggest sending off a stool sample for analysis. Anal disease like constipation, haemorrhoids (piles) can cause constipation.  Sometimes piles are visible but sometimes they are inside and can’t be seen, so a colonoscopy might be suggested. An allergy is always a possibility and patch testing may be required. The skin of the bottom is sensitive and can be easily irritated especially after defecation. Some faecal particles get trapped in the hair surrounding the anus and will contribute to the irritation.

Many patients opt for laser hair removal which seems to improve the condition. The skin can also be irritated by moist wipes, perfumed soaps, antiseptics for example Dettol and these should be avoided n this area. Bland emollients will be recommended by your Dermatologist. Sweating will also aggravate the condition.  Tight underwear or sitting in the the one position for long periods with no proper ventilation will exacerbate the condition for example lorry drivers.  

Management will depend on the underlying condition if there is one. Further investigations might be requested.  For most patients there is no underlying skin condition and they are managed with emollients, topical steroids and antihistamines with very good results, although relapses are common.