Foods to avoid when suffering from seborrheic dermatitis

Seborrheic dermatitis is a chronic inflammatory skin condition characterised by red patches covered with yellowish-white scales. This condition targets areas of the body that produce an excessive amount of sebum, thus creating an environment conducive to the growth of a fungus responsible for this disease: Malassezia. The scalp is almost always affected; other common sites (in order of frequency) are the face, particularly the eyebrows, the chest and intertriginous areas. Its histological appearance has strong similarities with psoriasis and constitutes one of the main difficulties in differential diagnosis.

Oily or seborrheic skin is the primary risk factor. The symptoms of seborrheic dermatitis are as follows:

• Red, scaly patches;

• Skin particles detaching from patches;

• Itching and pain at the site of the lesions.

Seborrheic dermatitis is widely recognised as one of the most common skin conditions, although estimates of its prevalence are limited by the absence of validated criteria for diagnosis or classification of its severity. An infantile form is known and affects 70% of newborns within the first 3 months of life, but generally disappears by the age of one year.

This skin condition is believed to be caused by the excessive proliferation of a fungus: Malassezia. Other factors such as hormones, diseases, or lifestyle could also play a part. Let's explore the dietary regimen to adopt in the case of seborrheic dermatitis.

Adopting a healthy diet can help combat seborrheic dermatitis. It is particularly advisable to avoid certain foods:

• Foods with high glycemic indices.

  This type of food is associated with hyperglycaemia, reactive hyperinsulinemia, and increased formation of insulin-like growth factor-1 (IGF-1). Insulin and IGF-1 stimulate sebaceous gland lipogenesis in vitro by increasing the expression of a transcription factor (SREBP-1) that regulates many genes involved in lipid biosynthesis. IGF-1 also plays a role in inducing the production of androgens. These in turn promote the growth of sebaceous cells and thus the production of sebum. Therefore, the consumption of high glycaemic index foods will only stimulate sebum production, thereby contributing to the proliferation of Malassezia. Among these foods, we can find: white bread, fried potatoes or even cooked carrots.

• Dairy products.

  Dairy products contain inflammatory fatty acids that can influence inflammatory responses and increase skin irritations. They are also rich in hormones such as oestrogens, progesterone, bovine insulin and IGF-1, which have the ability to stimulate the production of androgens. These androgens can impact the functioning of the sebaceous glands, leading to an excessive production of sebum, a condition known as hyperseborrhoea.

• Processed foods (fast foods, etc).

  This type of food is composed of "trans" fatty acids, which are associated with a high production of Insulin-like Growth Factor-1 (IGF-1). This factor increases the expression of a transcription factor (SREBP-1) that regulates many genes involved in lipid biosynthesis. It also plays a role in inducing the production of androgens that promote the growth of sebaceous cells, and thus the production of sebum.

• Alcohol.

  Frequent alcohol consumption increases the levels of certain hormones such as testosterone and estradiol, a form of oestrogen. This promotes the growth of sebaceous cells and consequently the production of sebum.

A healthy diet will enable you to limit the development of seborrheic dermatitis by soothing skin inflammation. The following foods should be prioritised:

• Foods with a low glycemic index:

  As previously discussed, foods with a high glycaemic index stimulate the secretion of sebum, which is the cause of the onset of seborrheic dermatitis. Therefore, replace them with foods with a moderate or low glycaemic index, such as whole grains, fruits and vegetables, legumes or even dried vegetables.

• Foods rich in omega-3:

  Foods rich in omega-3 inhibit the secretion of IGF-1, thereby reducing the overproduction of sebum. This consequently limits the proliferation of Malassezia and alleviates symptoms associated with seborrheic dermatitis. The oily fish (tuna, salmon, mackerel, etc...), the oilseeds (nuts, etc...), the avocados, the flaxseed, rapeseed and walnut oils are all foods rich in omega-3.

• Foods rich in antioxidants.

  Foods high in antioxidants play a protective role for the skin by neutralising free radicals, which can contribute to inflammation and exacerbate the symptoms of seborrheic dermatitis. Fruits and vegetables rich in antioxidants, such as citrus fruits, spinach, strawberries, cranberries, etc, are foods to prioritise in cases of seborrheic dermatitis.

SAKUMA T. H. & al. Oily Skin: An Overview. Skin Pharmacology Physiology (2012).

SANDERS M. G. H. & al. Association between Diet and Seborrheic Dermatitis: A Cross-Sectional Study. Journal of Investigative Dermatology (2018).

TAMER F. Relationship between diet and seborrheic dermatitis. Our Dermatology Online (2018).