• Chronic itchy, inflamed skin
• Skin is very dry, red, and scaly
• Scratching and rubbing lead to darkened and hardened areas of thickened skin with accentuated furrows, most commonly seen on the front of the wrist and elbows and the back of the knees
• Personal or family history of allergy
Eczema, also called atopic dermatitis, is a common condition that affects approximately 2 to 7% of the population. Current research indicates that eczema is, at least partially, an allergic disease because:
• Levels of serum IgE (an allergic antibody) are elevated in 80% of eczema patients
• All eczema patients have positive allergy tests
• There is a family history in two-thirds of eczema patients
• Many eczema patients eventually develop hay fever and/or asthma
• Most eczema patients improve with a diet that eliminates common food allergens
Eczema is also characterized by a variety of physiological and anatomical abnormalities of the skin. The major abnormalities are:
• A greater tendency to itch
• Dry, thickened skin that has decreased water-holding capacity
• An increased tendency to thickening of the skin in response to rubbing and scratching
• A tendency of the skin to be overgrown by bacteria, especially Staphylococcus aureus
Causes
The underlying abnormalities leading to eczema originate primarily in the immune system and structural components of the skin. For example, the allergy-related antibody IgE is elevated in up to 80% of patients with eczema due to increased activation of a specific type of white blood cell (type 2 T helper cells). In addition, mast cells (specialized white blood cells) from the skin of patients with eczema have abnormalities that cause them to release higher amounts of histamine and other allergy-related compounds compared with people without eczema. Histamine and other allergy-related compounds result in the inflammation and itching characteristic of eczema.
Another immune-system abnormality is a defect in the ability to kill bacteria. This defect in immune function, coupled with scratching and the predominance of the bacteria Staphylococcus aureus in the skin flora in 90% of eczema patients, leads to an increased susceptibility to potentially severe staph infections of the skin. There are also other immune defects in patients with eczema that lead to increased susceptibility to other infections of the skin, including infections caused by a herpesvirus and by common wart viruses.
A genetic basis for eczema has long been recognized. A family history of allergic disease such as eczema and asthma is a major risk factor. In addition to possible defects in immune function, one of the major genetic defects appears to be in the manufacture of filaggrin, a protein that facilitates proper integrity and moisture content of the skin.1
Therapeutic Considerations
Numerous studies have documented the major role that food allergy plays in eczema (see the chapter “Food Allergy”). Studies have also shown that breastfeeding offers significant protection against developing eczema as well as allergies in general.2,3 Interestingly, studies suggest that mothers of breastfed infants with allergies should avoid the common food allergens (especially milk, eggs, and peanuts and, to a lesser extent, fish, soy, wheat, citrus, and chocolate) themselves, to prevent traces of food antigens from appearing in their breast milk.4,5 Maternal avoidance of these common allergens is associated with complete resolution in the majority of cases.
In older or formula-fed infants, milk, eggs, and peanuts appear to be the most common food allergens that lead to eczema. In one study, these three foods were implicated in 81% of all cases of childhood eczema,6 while in another study 60% of children with severe eczema had a positive food challenge to one or two of the following: eggs, cow’s milk, peanuts, fish, wheat, or soybeans. One randomized, controlled trial found that in individuals with a positive reaction to eggs on a radioallergosorbent test, an egg-free diet was associated with improvement in the severity of eczema, with the greatest effect seen in those most severely affected.7 Although eggs are a major suspect, virtually any food can be the offending agent.8
Diagnosis of food allergy is usually best achieved by the elimination diet and challenge method. This approach is especially useful in childhood eczema. Elimination of milk products, eggs, peanuts, tomatoes, and artificial colors and preservatives results in significant improvement in at least 75% of cases.6-9 Laboratory tests used to identify food allergies in eczema are described in the chapter “Food Allergy.”
Some offending foods will have to be avoided indefinitely; others can be added back to the diet after 6 to 12 months. After one year, 26% of patients with eczema were no longer allergic to the five major allergens (egg, milk, wheat, soy, and peanut), and 66% were no longer allergic to other food allergens.10
Candida
An overgrowth of the common yeast Candida albicans in the gastrointestinal tract has been implicated as a causative factor in allergic conditions including eczema. Elevated levels of antibodies against candida are common in atopic individuals, indicating an active infection. Furthermore, the severity of lesions tends to correlate with the level of antibodies to candidal antigens. The bottom line is that elimination of candida results in significant clinical improvement of eczema in some patients.11,12 See the chapter “Candidiasis, Chronic” for information on how to prevent the overgrowth of candida.
Probiotics
Because the intestinal flora plays a major role in the health of the host, especially regarding eczema, probiotic therapy is particularly indicated. Studies show that administration of the probiotic Lactobacillus rhamnosus alone or in conjunction with Lactobacillus reuteri to infants with eczema and cow’s milk allergy demonstrates significant reduction of the severity of eczema.13–16
Essential Fatty Acids
In the past it was thought that supplementing the diet of eczema patients with evening primrose, borage, or blackcurrant oil (commercial sources of gamma-linolenic acid) might prove helpful. In fact, several double-blind studies with evening primrose oil (typically using dosages of at least 3,000 mg daily, providing 270 mg of gamma-linolenic acid) did show benefit.17–19 However, overall the therapeutic results appear to be more favorable with omega-3 oil supplementation from fish oils than with evening primrose oil. Several studies with evening primrose oil failed to demonstrate any therapeutic benefit over a placebo. In the largest of these studies and the one with the highest-quality methods, no benefit could be demonstrated for evening primrose oil.20 Similarly, one study of 140 people, including 69 children, showed few beneficial effects of borage oil.21
In contrast, fish oil supplements providing EPA and DHA are showing significant protective effects against allergy development as well as therapeutic effects in double-blind clinical trials.22,23 The difference in response is probably due to several factors. One is that fish oils contain primarily long-chain omega-3 fatty acids, which are further down the anti-inflammatory pathway, while evening primrose oil contains both omega-6 and omega-3 fatty acids and gamma-linolenic acid is at the beginning of the omega-3 anti-inflammatory chain. Some people, such as those with atopic disease, have poorer-functioning enzymes for the conversion to the anti-inflammatory prostaglandins.
Botanical Medicines
The use of botanical medicines in eczema can be generally divided into two categories: internal and external. Licorice (Glycyrrhiza glabra) appears to be useful in either application. Internally, licorice preparations can exert significant anti-inflammatory and anti-allergic effects. These benefits are perhaps best exemplified in several double-blind studies featuring a licorice-containing Chinese herbal formula.24 Interest in this formula by a group of researchers began after a patient with eczema experienced tremendous improvement after taking a decoction prescribed by a Chinese doctor. In one study, 40 adult patients with long-standing, refractory, widespread eczema were randomized to receive two months’ treatment consisting of either the active formula or a placebo decoction, followed by a crossover to the other treatment after a four-week washout period.25 The treatment group demonstrated significant improvement over the placebo group in clinical evaluation. In addition, of the 31 patients completing the study, 20 preferred the active formula, while only 4 preferred the placebo. There was also a subjective improvement in itching and sleep during the active treatment phase. No side effects were reported, although many subjects complained about the poor palatability of the decoction. Similar results were demonstrated in a double-blind study of children.26
QUICK REVIEW
• Eczema is an allergic disease.
• The underlying abnormalities leading to eczema originate primarily in the immune system and structural components of the skin.
• A genetic basis for eczema has long been recognized. A family history of allergic disease such as eczema and asthma is a major risk factor.
• Food allergy in susceptible individuals is the major cause of eczema.
• Allergies to milk, eggs, and peanuts account for roughly 81% of all cases of childhood eczema.
• Fish oils offer greater treatment benefits than evening primrose oil.
• Glycyrrhetinic acid, from licorice root, applied topically has shown advantages over corticosteroid creams.
TREATMENT SUMMARY
Effective management requires relief from and prevention of itching while the underlying abnormalities are being treated. Addressing food allergies is the first step. Follow the recommendations in the chapter “Food Allergy.”
Scratching is extremely detrimental because it breaks the skin, and this can lead to hardening of the skin as well as bacterial infection. The topical preparations mentioned below can be helpful in reducing itching.
Supplements
• High-potency multiple vitamin and mineral formula
• Vitamin E: 400 international units daily (mixed tocopherols)
• Fish oils: 1,000 to 3,000 mg EPA + DHA daily
• Probiotics: 5 to 10 billion viable lactobacillus and bifidobacteria cells per day
• Choose one of the following:
Enzymatically modified isoquercetin (EMIQ): 50–100 mg before meals
Grape seed or pine bark extract (>95% procyanidolic oligomers): 50–100 mg before meals
Topical Treatments
• Ceramide-containing moisturizers can be used to reduce water loss from the skin.
• Glycyrrhetinic-acid-containing commercial preparations may be helpful. Chamomile and oatmeal preparations are also popular. In particular, commercially available colloidal oatmeal products (e.g., Aveeno) contain starches and beta-glucans that have protective and water-holding effects, and their polyphenols (avenanthramides) are antioxidant and anti-inflammatory.
• Wash clothing with mild soaps only and rinse thoroughly.
• Avoid exposure to chemical irritants and any other agent that might cause skin irritation.
With regard to using licorice topically, the best results are likely to be obtained by using commercial preparations featuring pure glycyrrhetinic acid. Several studies have shown glycyrrhetinic acid to exert an effect similar to that of topical hydrocortisone in the treatment of eczema, contact and allergic dermatitis, and psoriasis. In one study, 9 of 12 patients with eczema unresponsive to other treatments noted marked improvement, and two noted mild improvement when an ointment containing glycyrrhetinic acid was applied topically. In another study, 93% of the patients with eczema who applied glycyrrhetinic acid demonstrated improvement compared with 83% using cortisone.27