Causes of sweating

Sweating can be a cancer symptom or may be due to cancer treatment. It can be very distressing. It can also be embarrassing if you are in a social situation.

Knowing more about the causes can help you understand why you might be sweating.

Why do we sweat?

Sweating is how our bodies keep cool. We have sweat glands in the skin over most parts of our body. They are in the layer of the skin called the dermis. The nerve cells in the dermis control sweating.

Although we don’t realise it, we are constantly sweating. The amount of sweat we make depends on:

• what we are doing
• our emotional state
• the temperature around our body

We sweat more when: 

• it is hot
• we exercise
• we are nervous, angry or upset
• we go through the menopause (women only)
• we are ill
• we take medicines that cause sweating

Causes of sweating

When you have cancer, things that may cause sweating include the following:

Infection

Infection is one of the most common causes of sweating in people with cancer. Infection can give you a high temperature, and your body sweats to try and reduce it. Treating the infection can control or stop sweating.

The cancer itself

Some cancers can cause you to sweat more than usual. These include:

• non-Hodgkin lymphoma
• Hodgkin lymphoma
• carcinoid tumours
• leukaemia
• mesothelioma
• bone cancer
• prostate cancer
• kidney cancer
• germ cell tumours
• advanced medullary thyroid cancer

People with advanced cancer of any type may also have sweating. 

Hormone changes

Changes in hormone levels can cause hot flushes and sweats. Your hormone levels may change because of the cancer itself or because of treatment. This includes treatments such as:

• surgery
• chemotherapy
• radiotherapy
• hormone therapy

Treatment for breast cancer can put women into an early menopause. For some women, this causes hot flushes and sweats. Women who have already had their menopause can have hot flushes again when they start hormone treatment.

Men can have hot flushes and sweating when they have hormone treatment for prostate cancer or breast cancer.

Medicines and cancer drugs

Sweating and hot flushes can be a side effect of some drug treatments, including chemotherapy and morphine.