Hair loss is a common concern for many people. In many cases, it is a form of alopecia (a medical term that describes different types of hair loss) such as hereditary, hormonal or localised hair loss.
However, hair loss can also be a symptom of something happening inside the body. Certain diseases, hormonal disorders or medications can temporarily or permanently affect hair growth.
This article focuses on hair loss caused by diseases and medical conditions, when hair loss is not a direct type of alopecia, but a result of an underlying health problem. Would you like to learn more about the different types of hair loss, such as hereditary or stress-related hair loss? Then read our detailed article ‘causes of hair loss’.
How can diseases cause hair loss?
Diseases can cause hair loss by disturbing the balance in your body. Some conditions affect hormone levels, others cause inflammation or lead to a lack of important nutrients.
A few common examples are:
- Hormonal changes, such as with thyroid problems or PCOS.
- Inflammation or autoimmune reactions, such as lupus or bowel diseases.
- Nutrient deficiencies, such as those caused by liver, kidney or intestinal disorders.
- Medication, which can slow down the hair growth cycle or cause hair loss as a side effect.
Diseases that can cause hair loss
Inflammatory and autoimmune diseases
Lupus is an autoimmune disease that can affect different parts of the body, including the skin and hair. Because of this, hair loss can appear in patches or be more widespread.
Inflammatory scalp conditions such as lichen planopilaris or psoriasis can also damage the hair follicles. Psoriasis is often recognised by red, scaly areas that can itch or feel sore. If the inflammation is not treated in time, the hair can become thinner or fall out in those areas.
Hormonal and metabolic diseases
Hormonal imbalances play an important role in many types of hair loss.
- Thyroid disorders: an overactive or underactive thyroid can affect hair growth, making the hair thinner across the entire scalp.
- PCOS (Polycystic Ovary Syndrome): this hormonal condition in women is caused by an overproduction of androgens (male hormones). It can lead to thinner hair on the crown or a wider parting.
- Diabetes: long-term changes in blood sugar levels can reduce blood flow to the hair roots, slowing down hair growth.
Chronic diseases and nutrient deficiencies
Kidney diseases
Kidney diseases, also known as chronic kidney disease (CKD), can reduce the kidneys’ ability to filter waste products from the blood. Hair loss is one of the possible symptoms, along with tiredness, weight loss and loss of appetite. The hair loss is usually diffuse and spread over the entire scalp. Although the exact link is not yet fully understood, it is believed that long-term kidney disease can lead to a lack of important nutrients such as iron and protein. These nutrients are essential for healthy hair growth.
Liver diseases
Liver diseases can also affect the condition of your hair. The liver plays an important role in breaking down waste products in the body. When the liver does not function properly for a long time, it can lead to a lack of vitamins and minerals such as biotin and zinc. This can make the hair thinner or more brittle. Other diseases that can cause both hair loss and tiredness include thyroid disorders, autoimmune diseases and cancer.
Infectious diseases
Lyme disease
Lyme disease is a bacterial infection that is spread through tick bites. Although the disease is best known for causing symptoms such as fever, headache and tiredness, it can also lead to hair loss. The exact connection is not yet fully clear, but it is believed that the inflammation caused by the infection can temporarily disturb the hair growth cycle. In rare cases, the immune system may become overactive, which can also lead to hair loss. If you are experiencing both Lyme disease and hair loss, it does not always mean that the two are directly related.
Tinea capitis
Tinea capitis is a fungal infection of the scalp that mainly occurs in children. This infection causes round, scaly bald patches and sometimes inflammation. The infection is contagious and can spread through contact with people, animals or contaminated objects.
Sexually transmitted infections (STIs)
Some infections can cause hair loss. Syphilis, for example, can lead to patchy hair loss during the second stage of the infection. Other infections such as HIV, chlamydia or gonorrhoea do not directly cause hair loss, but the medicines used to treat them can sometimes have this as a side effect.
Inflammatory bowel diseases
Crohn’s disease
Crohn’s disease is a chronic inflammatory condition that affects the digestive tract. Although the disease mainly affects the intestines, the inflammation and the medicines used to treat it can also influence hair growth. Hair loss in people with Crohn’s disease may be caused by inflammation in the body that temporarily stops the hair from growing. In addition, medicines used to treat Crohn’s, such as mesalazine, azathioprine and infliximab, can have hair loss as a side effect.
Ulcerative colitis
Ulcerative colitis is similar to Crohn’s disease but mainly affects the large intestine. Hair loss can also occur in this condition due to long-term inflammation or as a side effect of medication.
Coeliac disease (gluten intolerance)
Coeliac disease is an autoimmune condition in which the body reacts too strongly to gluten. This reaction damages the lining of the small intestine and makes it harder for the body to absorb nutrients. Many people with coeliac disease have deficiencies in iron, zinc and vitamins, which can also affect hair growth. Once gluten is removed from the diet and nutrient absorption improves, the hair usually grows back.
Medications that can cause hair loss
Some medications can cause hair loss as a side effect. This can be temporary or continue for as long as the medication is being used. Examples include:
- Chemotherapy (temporarily stops hair growth)
- Antidepressants or blood thinners
- Thyroid medication and hormonal contraception
- Immunosuppressants (such as azathioprine and infliximab) used for autoimmune diseases
The amount of hair loss differs from person to person and depends on the dose, how rare the side effect is, and the length of the treatment. In most cases, the hair grows back once the medication is stopped or adjusted.
Is the hair loss temporary or permanent?
In most cases, the hair grows back once the disease is under control or the treatment is stopped. However, in conditions where the hair follicles become inflamed or damaged for a long time, such as in some autoimmune diseases, the hair loss can be permanent.
Conclusion
Hair loss can be caused by many different diseases and conditions that temporarily or permanently upset the balance of the body. Autoimmune diseases, hormonal disorders, infections or nutrient deficiencies can all affect hair growth, as can certain medications with hair loss as a side effect. In most cases, the hair grows back naturally once the underlying cause is treated or the body is back in balance. However, if the hair loss continues, it is wise to seek medical advice to identify the exact cause and support recovery.
Sources
British Association of Dermatologists. (z.j.). Hair loss and systemic disease. Bad.org.uk. https://www.bad.org.uk
Journal of Cutaneous Pathology. (z.j.). Case of inflammatory hair loss associated with Lyme disease. Wiley Online Library. https://onlinelibrary.wiley.com
