by Dr. Madalene Heng MD, FRACP, FACD, FAAD

Identifying Factors

Identifying the Factors that Lead to Injury 

Although the psoriatic gene is present at birth, the patient does not develop psoriasis until precipitated by trauma, allergic reactions and infections. The location of psoriasis gives a clue as to what precipitates or aggravates the disease:

1. Scalp

  • Pityosporum ovale: a lipophilic yeast which feeds on the oils secreted by sebaceous glands (Heng MCY et al. Correlation of Pityosporum ovale density with clinical severity of seborrheic dermatitits as assessed by a simplified technique. J Am Acad Dermatol 1990:23:82-86). The population of P. ovale is increased by increased oil production, which is aggravated by stress, and by lactose intolerance.
  • Black/brown hair dyes (paraphenylene diamine)
  • Nickel from touching nickel filings from coins and keys, brought to the scalp by the fingers
  • Staphylococcus aureus colonizing the porous skin scales
These patients may have lesions on the face (hair-line, eyebrows, paranasal cheeks), ears and behind the ears.

2. Trunk and Limbs 

The affected areas are usually in areas in contact with elastic in clothing (bras areas, around waist, areas in contact with socks/stockings, and in areas in contact with leather products such as upholstery in cars/chairs, as well as skin in contact with black/brown dyes (hair dyes during showers, black/brown clothing and socks, and black/brown upholstery.

The common allergens are:
  • elastic antioxidants in elastic, latex, spandex underwear, clothing and socks
  • paraphenylene dyes in black/brown clothing and hair dyes
  • nickel from jewelry, coins, and keys
  • leather products 
  • Staphylococcus aureus/MRSA bacterial superinfection.
3. Hands and Feet 

  • Fingers, especially around the nails (nickel from coins/keys contacted by putting hands in pockets containing coins and keys.
  • Web spaces and dorsum of hands and fingers: latex gloves, nickel, detergents, trichromates in gasoline/leather products/printer's ink/ motor oils/ brake fluid/ lubricating oils/ cement.
  • Palms: leather/black steering wheel cover, handles of tennis rackets, golf clubs, paints, varnishes, glues etc.
  • Dorsum: trivalent chromates in leather shoes/foot-wear, black or elastic material in shoes
  • Soles: leather insoles, neoprene glues that glue insoles to sock lining.

Treatment: use plastic wrap to insert between foot-wear and skin of foot.

4. Flexural areas (axilla, groin, perianal)

Aggravating factors are
Candida albicans

Flexural psoriasis may be aggravated by obsesity, diabetes, but also by lactose intolerance, which results in zinc deficiency (Heng MCY. Acrodermatitis associated with zinc deficiency: features and postulated mechanism. Australas J Dermatol 1988;39:169-193). Since human mother’s milk contain galactose and cow’s milk, lactose, we cannot secrete enough lactases in the small intestine to digest the lactose we ingest. As a result, the lactose spills into the colon, and, through increasing the osmotic pressure in the colon, interferes with the colonic bacteria. The interaction of the colonic bacteria with undigested lactose in the colon results in the death of colonic bacteria, which release lipopolysaccharides (L:PS) from the bacterial membranes. LPS is a potent superantigen, which activates large numbers of T lymphocytes, and stimulates the formation of high levels of TNF-alpha, which causes worsening of psoriasis

The patients should substitute soy products for lactose containing foods, and take calcium and vitamin D supplements instead. They may also have goat cheese, which does contain lactose, but is more digestible.

Download Article"Results of Combining Phosphorylase Kinase Inhibition with Removal of Precipitating Factors in Large Cohort of Psoriatic Patients: A Proof of Concept Study" Journal of Cosmetics, Dermatological Sciences and Applications, 2011, 1, 79-94. MCY Heng, Judith Harker, MK Heng.