Many studies indicate that stress, local skin injury and infections can act as a trigger for psoriasis in genetically predisposed individuals.
Stress as Psoriasis Trigger
Psoriasis is more stress sensitive than many other skin diseases. Many stressful events of daily life may exacerbate psoriasis. The disease itself may cause a 'reactive depression' in the patient which could further exacerbate his psoriasis.
A number of studies have shown that psychological stress is often caused by psoriasis, and also can be a factor in psoriasis flare ups. Thus stress is a psoriasis trigger and psoriasis is a stress trigger.
Conversely, psychological stress can affect the course of the disease as well as contribute to psychological problems such as depression, anxiety, and unfocused anger. The way stress affects the patient varies from individual to individual; the most common manifestations are psychological depression, anxiety, and obsessional behaviours.
The way in which stress, depression and anxiety influence the course of psoriasis is not known. Some studies suggest that the influence may be through an effect on the immune system. Stress has far reaching effects not only on the immune system, but the neuro-endocrinological systems as well.
Local Skin Injury as Psoriasis Trigger
Koebner phenomenon, also known as isomorphic response, refers to the induction of lesions following local trauma or injury to the skin.
Superficial trauma to the epidermis alone will not induce the new lesions; injury to the upper part of dermis (papillary dermis) is necessary for the Koebner's to occur. Insult to the skin may be of any kind, e.g. physical (cuts), chemical (burns), mechanical (rubbing), allergic (contact dermatitis) etc.
There have been many case reports of Koebner phenomenon developing at sites of surgical wounds, sunburn, chickenpox scars, vaccination ulcers and other skin eruptions.
It usually occurs within 7 to 14 days of injury to the dermis; the interval may vary from 3 days to 3 weeks. Koebner phenomenon has also been reported at sites of bites (insects, animals), drug reactions, herpes zoster, and skin tests also.
Research shows that about 50% of people with psoriasis experience the Koebner phenomenon.
About 10% of psoriasis patients develop a new psoriatic lesion each time the skin is injured. The likelihood of developing the Koebner phenomenon may increase when psoriasis lesions are already present.
Infections as Psoriasis Trigger
Studies show that some infections can trigger psoriasis. Dermatologists have seen people with a family history of psoriasis get strep throat and develop their first psoriasis lesions two weeks later. Strep throat often precedes an outbreak of guttate psoriasis. Inverse psoriasis is frequently aggravated by a thrush infection.
Common infections that can trigger psoriasis are:
- Candida albicans (thrush)
- Human immunodeficiency virus (HIV)
- Staphylococcal skin infections (boils)
- Streptococcal pharyngitis (strep throat)
- Viral upper respiratory infections
Treating the infection in many cases lessens or clears the psoriasis.
Next: Medications and Climate as Psoriasis Triggers.
Reference
Psoriasis, in Rook’s Textbook of Dermatology, 7th Edition, 2004
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