What Causes Psoriasis?
Nearly every day, we are asked “what causes psoriasis?” The answer is complicated, includes many factors, and has not been completely worked out. Here is a summary of what we know so far.
Exactly what causes psoriasis is not fully understood but there is a lot of active research into this area. The immune system is involved and appears to be overactive in a way that causes inflammation. This also causes growth of extra blood vessels within the skin (causing the red colour) and increased turnover of the skin cells (causing the scaling and thickening of the skin).
- Genetic influences
- Like most diseases, psoriasis is influenced by inherited characteristics. Up to 50% of people with psoriasis will know of another affected family member. Patients with a family history of psoriasis tend to develop psoriasis earlier in life than those without a family history.
- Stress
- Physical and emotional stress may precipitate psoriasis and are hard to avoid.
- Infection
- Infections may cause flares of psoriasis. Sometimes, treatment of the infection may result in clearing or improvement of the psoriasis.
- Sreptococcal throat infections (tonsillitis) may cause guttate psoriasis.
- Candida infections (thrush) may aggravate flexural psoriasis.
- Malassezia yeasts may have a role in sebopsoriasis.
- Injury
- Psoriasis localises around the site of physical, chemical, electrical, infective and inflammatory injury as it heals (the Koebner phenomenon). Less often, psoriasis may localise to old scars.
- Hormones
- The relationship of hormones to psoriasis is unclear. Post-puberty is a peak time for the onset of psoriasis. Pregnancy may also have an effect on the severity of the psoriasis; it usually improves with the potential for worsening after the birth of the baby, but the reverse can occur. Psoriasis does not affect the unborn baby.
- Medications
- Several medications can precipitate or aggravate psoriasis:
- Lithium,an antidepressant (supplements of inositol 6g daily may reduce this tendency)
- Beta blockers (used to treat high blood pressure)
- Anti-malarials e.g. hydroxychloroquine
- Stopping oral corticosteroids
- Stopping strong topical corticosteroids.
- Ultraviolet light
- Sunlight is usually beneficial for psoriasis (except in sun sensitive / photosensitive psoriasis).
- Alcohol and smoking
- There is an association between increased alcohol intake and smoking and the development of severe psoriasis.
Source: Dermnetnz.org