Chronic dermatitis + ‘itch-scratch’ cycle + stress
Seborrhoeic dermatitis (esp.), eczema
Contact dermatitis: clothing and perfumed toiletries
Irritation from excessive moisture and faecal discharge/soiling (esp. elderly)
Serious disorders not to be missed
Extramammary Paget disease
Sexually transmitted infections, e.g. syphilis
Pinworm (threadworm) (esp. children)
Psoriasis (look for fissures in natal cleft)
Overzealous hygiene (e.g. OCD)
Post-diarrhoea esp. chronic or recurrent
Local anorectal conditions (e.g. piles, fissures, fistulas, skin tags, warts)
Is the patient trying to tell me something?
Psychological factors: stress and anxiety, fear of cancer.
This includes past history, especially chronic dermatoses (esp. seborrhoeic dermatitis and contact dermatitis), diabetes, chronic diarrhoea (e.g. Crohn disease, coeliac disease) and psychological disorders. Enquire about lifestyle factors such as excessive sweating, sports activity and habit scratching.
General inspection of skin and anorectal area. Skin changes can vary from minimal signs to marked pathology that can show linear ulceration, maceration or lichenification
A full anorectal examination is necessary
Pruritus ani is worse at night, during hot weather and after exercise.
It is seen typically in adult males with considerable inner drive, often at times of stress and in hot weather when sweating is excessive.
In children pinworm infestation should be suspected.