Why Do Some People Have Dandruff?

It is difficult when surveying current dermatology literature to identify much of a clinical difference between severe dandruff and seborrheic dermatitis. Often the terms are used interchangeably. Because the apparent causes of both these conditions—Malassezia fungi, sebaceous secretions, and individual sensitivity—and because the treatments that are effective in either condition are common to both, we are prone to talk of them as effectively one and the same.

Seborrheic dermatitis/dandruff—where it's at…

Seborrheic dermatitis in adults most often manifests as a scaly, itchy, red rash on the scalp, but also in some sufferers affects the skin around the nose, and on the chest—in the folds under the breasts in women, or on the skin of the sternum in men, particularly around the hair follicles.

A causal connection between the fungus Malassezia (primarily the species M. restricta and M. globosa) and severe dandruff or seborrheic dermatitis is largely based on the ability to isolate Malassezia from seborrheic lesions on the scalp or body, and the therapeutic effectiveness of antifungal treatments in killing Malassezia. A reduction in the number of Malassezia cells almost invariably leads to improvement in the condition, and the only link between the varied treatments most effective at reducing scaling and itch is their antifungal properties.

Complicating this picture, however, is the fact that the number of Malassezia cells one might "possess" doesn't necessarily translate into a case of dandruff. Malassezia is a common and normal microbe among many that populate the human body. The fungus metabolizes the triglycerides and fat contained in the sebum secreted from the skin's sebaceous glands for its survival. An individual may have fewer Malassezia cells relative to someone with many, yet the person with fewer cells may suffer the case of dandruff while the other remains dandruff-free. What's the difference?

Altered Skin Barrier & Irritating Fatty Acids

Why do only some people have dandruff? This is a question explained not so much by simple presence of contributing elements but by variations in individual response to those conditions. Consider the following.

Symptomatic individuals appear to react to irritating free fatty acid metabolites released by Malassezia as a result of their consumption of sebaceous triglycerides. Oleic acid is one such fatty acid metabolite, studied as one of several fatty acids behind the scaling and itch of severe dandruff. When researchers topically exposed individuals known to suffer dandruff, as well as those without dandruff, to oleic acid, an unsaturated fatty acid, while controlling the number of Malassezia cells present, the individuals with a predisposition to dandruff developed scaly, itchy lesions. Those not predisposed to dandruff were unaffected when oleic acid was applied.

The difference in an individual's reaction to the Malassezia metabolite appears to be that people predisposed to severe dandruff also appear to have an underlying permeability barrier deficiency. An abnormality in the stratum corneum—the outermost layer of skin consisting of dead, flattened squamous cells of keratin and lipids which form a permeable protective barrier—allows irritating fatty acids to form the scaly and itchy lesions typical of dandruff by some mechanism.

It is not known precisely how fatty acids are involved in forming the scale and itch of dandruff, but improving the conditions of this barrier is a likely therapeutic approach to treating and controlling severe dandruff. Reducing the number of Malassezia cells and their metabolites, while improving the ability of the skin to resist the effects of the metabolites, is likely to improve the symptoms of severe dandruff.

Diet & Homeostasis

Improving the condition of your skin is likely to take you at least part of the way toward minimizing symptoms of severe dandruff. A good first step involves deliberate changes in how you eat—increasing your intake of foods known to support healthy skin, including a healthy scalp—and ingesting probiotic supplements. If you've already embarked on dietary changes, consider each new day an opportunity to contribute to your skin's health. Sticking with a diet that supports healthy skin may be more important than simply "trying" a skin-healthy diet because what you are trying to achieve is better homeostasis. Probiotic supplements provide the body with friendly living microorganisms that are believed to help the body regulate systemic immune response that contributes to allergenic and inflammatory skin conditions.

The American Heritage Medical Dictionary defines homeostasis as: "The ability or tendency of an organism or a cell to maintain internal equilibrium by adjusting its physiological processes." Following a skin-healthy diet consistently over a period of time is likely to be more successful than a short-term trial, because as one shifts the equilibrium of one's physiological processes in the direction of healthier skin, those processes become the new normal, and the homeostasis achieved is likely to produce the most optimal effects—that is, the healthiest skin.

Foods & Nutrients Helpful for Dandruff

Equipped now with better understanding of why adding foods to your diet can support healthy skin, let's review some specific foods, probiotics supplements, and nutrients reported to be helpful.

Biotin is a ubiquitous substance in nature, showing up in many plants, but biotin is also a vitamin-like nutrient crucial to the metabolism of fatty acids, amino acids, and glucose. Biotin deficiency is rare given its fortunate availability in nature, but does occur nevertheless and is associated with many serious clinical conditions including seizures, mental retardation, and birth defects. Soy is rich in biotin, as are garlic, American ginseng, oats, barley, Asian ginseng, avocado, cottonseed, alfalfa, sesame, corn, fava beans, peas, lentils, and elderberry.

Alfalfa is also notable for the antidandruff activity possessed by the salicylic acid, selenium, and zinc it contains, additives found in many dandruff remedies. Alfalfa in combination with carrots and lettuce, both supplying antidandruff activity through supplying selenium, sulfur, and zinc, is mentioned in Ayurvedic remedies for dandruff. Several other foods, such as Brazil nuts, pumpkins, and plums containing lecithin, or parsnips, radish, and cabbage containing sulfur are useful in a diet that moves us toward a healthier skin homeostasis.

Natural Remedies & Folk Medicine for Severe Dandruff

Some time-tested natural remedies used to relieve the symptoms of severe dandruff include concoctions to be used either before a shampoo and massaged into the scalp, or mixed with a good herbal shampoo. Among the best known is ti-tree oil, which is extracted from Melaleuca alternifolia, a species of paperbark native to Australia. Ti-tree (commonly known as tea tree) oil contains organic terpenes that facilitate the oil's penetration and antiseptic activities into the upper layers of the scalp, disinfecting deeper than other surface emollients.

"Scarborough Shampoo," is so called for the therapeutic effects of sage (containing menthol, salicylic acid, selenium, zinc), rosemary (zinc, pantothenic acid, niacin), and thyme (selenium, zinc) that tinctures of each added to a good herbal shampoo can supply.

Two tablespoons of ginger root juice, squeezed from fresh-grated roots, mixed with three tablespoons of sesame oil and a half-teaspoon of lemon juice, then applied to the scalp three times a week represents an Egyptian remedy taken from Heinerman's Encyclopedia of Fruits, Vegetables and Herbs by medical anthropologist John Heinerman, PhD.

Both comfrey (Symphytum officinale L.) and plantain (genus Plantago) contain allantoin, a substance with antidandruff properties. Tinctures of either can be added to an herbal shampoo or, in the case of plantain, a strong tea made from the herb is suggested as a hair rinse.

Warm vinegar or apple cider applied directly to the scalp before shampooing has been used over the years as an old folk remedy for dandruff, and in its simplicity bears consideration today.