Psoriasis which resists treatment

The forms of psoriasis which are resistant to treatment affect around 10% of patients. These may be localised or spread over the body. They include psoriasis which previously improved with treatment and subsequently became resistant without an obvious cause; psoriasis which has not improved with local treatment; and psoriasis that reacts badly to phototherapy.
 
In some cases, psoriasis turns out to be resistant because the patient has not followed instructions regarding therapy due to the constraints this places on his or her lifestyle. It should be noted that in children, an infectious agent may cause forms of psoriasis that are resistant to treatment, and especially those which tend to recur.

The dermatologist should question the patient closely in order to identify the factors which led to the psoriasis becoming resistant. In particular, this means listing previous therapies, ascertaining if exposure to the sun improves lesions or not, and checking if the patient has started taking any new drug for another condition. This information will allow the dermatologist to suggest another local or systemic treatment, taking into account any possible side effects.