Eczema and Weight

Introduction

Of the diseases commonly misunderstood and underestimated, eczema often happens to be one of them, with many misconceptions surrounding it. That it is merely a skin rash and contagious are some of the more common myths about eczema. The exact cause of eczema is not known. Still, a  popular controversy is that eczema may be a lifestyle-related disease caused by obesity, and that changes to diet and increased physical activity may improve symptoms. 

What is eczema?

Eczema is the name of a group of infections that causes dry, irritated, and inflamed skin that becomes sore. The most common form of eczema is atopic eczema (atopic dermatitis), a chronic inflammatory skin disease whereby the skin becomes dry, itchy, and cracked. The other types of eczema are: discoid eczema; contact dermatitis; varicose eczema; seborrheic eczema; and dyshidrotic eczema. 

The exact causes of eczema remain unclear. However, they are most likely multifactorial, and the disease may be caused by genetic and/or environmental factors, such as an adverse reaction to allergens (substances that cause allergies).¹

Symptoms

According to the NHS, atopic dermatitis occurs most commonly in children, with the symptoms appearing during infancy. However, the symptoms have been known to appear for the first time in adults as well. 

The severity of atopic eczema varies from person to person. It occurs most commonly on the hands (especially fingers), face, scalp, backs of the knees, and the elbow pit or the inside of the elbow. For the disease to be diagnosed as atopic eczema, the skin around these areas should have been dry and visibly irritated (appearing red) for at least 12 months. 

Those with a milder form of the disease usually have small areas of the skin that become dry and itchy. In more severe cases, inflammation can occur in the skin, with the inflamed skin becoming extremely itchy and sore. The inflamed skin usually appears red on lighter skin and darker brown, purple, or grey on darker skin. In some cases, a secondary infection can also happen in the skin.¹

Obesity cannot cause eczema

Eczema is believed to be an autoimmune disease. An autoimmune disease is a condition where a dysregulated immune system targets the host’s tissues, or to put simply, the immune system makes a mistake and attacks the body’s own healthy tissues and organs. The immune system recognises the proteins belonging to the self (self-proteins or self-antigens) as foreign and mounts an attack. A characteristic of autoimmune diseases is inflammation in the body of the patients.

The term atopic means sensitive to allergens. It is believed that an allergic response to things such as food, soaps, detergents, and stress may trigger the symptoms of atopic eczema. An overactive response of the immune system mediated by IgE antibodies to these allergens resulting in inflammation is believed to cause eczema. 

The idea that eczema, specifically atopic dermatitis, may be an autoimmune disease came about when scientists observed immune reactions to self-proteins in patients with atopic dermatitis. A high number of IgE reactive autoantigens have been identified specifically for eczema. Since atopic eczema involves allergic reactions, the word autoimmunity is not generally used. Instead, another term, autoallergy (study of autoimmunity caused by IgE antibodies or autoimmunity accompanying an allergic reaction), is used with atopic eczema.³

As eczema is an autoimmune condition involving an immune system gone haywire, it challenges the notion that obesity might be a direct cause of eczema. Although studies initially have shown that in obese teenagers there is an increased severity of eczema symptoms, new research has brought to light that the connection may not be quite as straightforward as previously imagined. 

In a recent study conducted amongst European populations, scientists tried to find the odds that adults with eczema would be obese vs. adults without eczema. It was seen that people with eczema had a slightly higher chance of being overweight. However, there was no evidence indicating that obesity led to patients having severe eczema. It was also seen that approximately 50% of the people were obese, regardless of eczema. 

In another study conducted in the US, it was seen that patients with moderate atopic eczema were obese. Still, there was no link between severe atopic eczema and obesity.²

Obesity is a pro-inflammatory state

Obesity is the accumulation of excess fat which is stored in adipose tissues of the body. Several studies have shown that an increase in BMI leads to an increase in inflammation in the body. In obesity, the adipose tissue mass increases, and the tissues become dysfunctional and release pro-inflammatory molecules that cause inflammation. 

These molecules include cytokines such as interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-ɑ). The systemic inflammation seen during obesity is not just caused by adipose tissues. IL-6 produced by the adipose tissue acts on the liver and induces it to release another inflammatory marker, CRP. The levels of anti-inflammatory hormone adiponectin, also produced by adipose tissues, are lowered during obesity, leading to an environment that is pro-inflammatory.^4,5

State of pro-inflammation increases the chance of eczema flare-up

Obesity tends to favour a pro-inflammatory environment, and eczema is a chronic inflammatory disease. It manifests itself in different forms, with some patients showing little to no change, and in others there is a period of absence of symptoms followed by a sudden increase in illness, known as ‘flares.’ Obesity results in the increase of the mass of adipose tissues, which in turn produce leptin or oestrogen that stimulates the production of pro-inflammatory cytokines which disrupt the skin barrier and predispose patients with eczema to skin inflammation and intense scratching. The scratching can lead to skin lesions, which further leads to barrier disruption that causes the release of other cytokines that mediate a Th2 (T-helper cells help to regulate immune responses) response characteristic of eczema. 

Obesity, by itself, reduces the epidermal (skin) barrier function as increased sweating and blood pressure lead to water loss from the skin and changes to the lipid structures in the epidermis.^2,6

Summary

The exact reason why eczema happens still remains a mystery, but scientists believe that multiple factors - genetic and environmental - play a role. It is thought that the disease gets triggered by an overwhelming allergic response to some substance that leads to the development of an autoimmune condition. Many have also tried to find out if this is a lifestyle related disease, and it has been seen that there is a link between eczema and obesity. To say that obesity causes eczema would be stretching the truth, but it may predispose individuals to eczema. As the mass of adipose tissues increases in obesity and becomes dysfunctional, they release inflammatory molecules called cytokines that disrupt the skin barrier and cause skin inflammation and lesions, which further initiate an immune response. Although obesity may not be the reason why one develops eczema, getting rid of the extra weight might help in managing the symptoms of the disease. Exercising and maintaining a good diet will also reduce the risk of complications such as cardiovascular disease.