The invisible protective network in your body

What is meant by the lymphatic system?

The lymphatic system is a network in the body made up of lymphatic vessels, lymph fluid (lymph), lymph nodes and lymphatic organs such as the spleen, tonsils, bone marrow and thymus. It runs throughout the body and connects different tissues and organs. 

Similar to the blood vessel system, the lymphatic system is a transport system, but instead of blood it carries lymph - a clear fluid that removes metabolic waste products and excess tissue fluid from body tissues. Lymphatic vessels have valves that ensure lymph flows toward the heart, where it is ultimately returned to the bloodstream.

Another essential component is the lymph nodes, small bean-shaped nodules along the lymphatic vessels that filter lymph and house important cells for the immune response. This structure makes the lymphatic system a central part of the body's defence system, involved in removing foreign substances and protecting the body from harmful invaders.

What are the functions of the lymphatic system?

The lymphatic system fulfils several essential functions in the body. On the one hand, it is responsible for immune defence by recognising and neutralising pathogens such as bacteria and viruses. In lymphatic organs - such as lymph nodes and tonsils - specialised defence cells are located that primarily intercept harmful foreign substances in the throat and neck area. Abnormal or altered cells, for example cancer cells, are also recognised and eliminated by the lymphatic system to prevent their spread through the body.

In addition, the lymphatic system regulates the fluid balance in tissues. The lymph fluid, called lymph, transports excess tissue fluid back into the bloodstream, thus maintaining a stable volume of fluid in body tissues. This function is important to prevent fluid accumulations, so-called lymphoedemas. Lymph flow is further supported by muscle movements, which can significantly accelerate it during physical activity.

Another central function of the lymphatic system is the transport of dietary fats. Unlike other nutrients, fats are absorbed after digestion via the lymphatic system because they are not directly water-soluble. Lymphatic vessels transport these fats, which relieves the blood and helps maintain its flow properties.

Besides these main functions, the lymphatic system also serves tissue cleansing and supports general defence against infections and toxins. The various lymphatic organs such as the spleen, tonsils and the lymphatic tissue of the gut are specifically adapted to produce defence cells and ensure a coordinated immune response that strengthens and protects the body against pathogens.

What do lymph nodes do?

Lymph nodes play a central role in the defence system and are crucial for the fight against pathogens. They act as filtration stations through which lymph fluid drains from tissues. This fluid contains, in addition to fats, proteins and cells, potentially harmful substances such as viruses, bacteria and cancer cells. Lymph nodes contain specialised immune cells such as macrophages and lymphocytes that recognise and neutralise these foreign substances.

In addition, lymph nodes are an important activation centre of the immune system. When pathogens enter the lymph nodes, the immune response is mobilised. The defence cells contained within produce antibodies and trigger an immune reaction. These cells then leave the lymph node and travel via the blood to the site of infection where they combat the invaders.

Lymph nodes are also involved in the surveillance and control of tumour cells. If cancer cells spread through the lymphatic system, they are usually detected first by the lymph nodes, which enables early diagnosis and treatment. An affected lymph node is referred to as a «Wächterlymphknoten".

What diseases affect the lymphatic system?

Lymphatic system diseases can significantly impair the body. The most common conditions include lymphoedema, lymphadenopathy, lymphomas and lymphangitis.

A lymphoedema occurs when lymph fluid accumulates in tissue and causes swelling, usually in the arms or legs. It can be genetic (primary) or arise from external factors such as surgery, radiation or inflammation (secondary). Lymphadenopathy refers to enlargement of the lymph nodes, which often occurs as a reaction to infections, autoimmune diseases or cancer. Although lymphadenopathy is not a disease in its own right, it indicates underlying health problems.

Lymphomas are cancers that originate from lymphocytes, a subgroup of white blood cells. Lymphangitis is an inflammation of the lymphatic vessels, often caused by bacterial infections, and is associated with symptoms such as skin redness, fever and general malaise.

The symptoms of these conditions vary but commonly include limb swelling, enlarged lymph nodes, fatigue, fever, unexplained weight loss and skin changes. Early detection and targeted treatment are essential to stabilise health and avoid complications.

What causes swollen lymph nodes?

Swollen lymph nodes usually occur in response to infections, inflammation or other health problems. When the immune system reacts to pathogens, it collects defence cells in the lymph nodes, causing them to swell. This swelling is often a sign that the body is fighting an infection or illness.

A common cause of swollen lymph nodes are viral infections such as infectious mononucleosis, measles, rubella or cytomegalovirus. An HIV infection can also cause lymph node swelling. Bacterial infections are also among the most frequent triggers, including tonsillitis, syphilis, tuberculosis, Lyme disease and cat-scratch disease. Oral infections such as gum inflammation or purulent abscesses can also lead to swollen lymph nodes.

In rarer cases, cancers such as leukaemia, lymphomas or lymph node metastases can be the cause of swollen lymph nodes. Autoimmune diseases like rheumatoid arthritis or systemic lupus erythematosus can also cause lymph node enlargement. COVID-19 and coronavirus vaccination have also been associated with swollen lymph nodes, as the body responds to the virus or vaccine with an immune reaction.

Typically, lymph node swelling resolves once the underlying cause is treated. If the swelling persists or is accompanied by other symptoms, a doctor should be consulted for an accurate diagnosis.

Treatment: What to do about swollen lymph nodes?

Treatment of swollen lymph nodes is primarily determined by the underlying cause. Warm, moist compresses and rest can relieve pain. Adequate fluid intake supports healing; if needed, pain relievers such as ibuprofen may be taken. For minor infections like a cold, keeping the throat warm can be helpful.

The doctor will examine the lymph nodes by palpation and may order blood tests or a biopsy to clarify the cause. In rare cases, e.g. when cancer is suspected, imaging studies are required to assess the extent of the disease.

Get your lymph flowing: useful tips

• Move regularly to prevent lymph stasis and activate the lymphatic system. Activities particularly beneficial include swimming, cycling, yoga or walking. These support the lymph capillaries and the lymphatic vessel system, as muscle activity and pressure from arteries and capillaries assist lymph flow toward the venous angle.
• If you sit for too long, foot exercises are recommended: raise and lower your feet or make circular movements in the ankle. 
• Drink at least 1.5 to 2 litres of water daily. Good hydration helps the lymphatic system transport metabolic products and toxins. Always keep a bottle of water within reach.
• Maintain a healthy diet with plenty of vegetables and fruit and less salt. Some products like ham, sausages, canned fish, ready meals and liquorice contain too much salt and contribute to fluid retention.
• Use a natural-bristle brush and brush gently towards the heart. Start at the feet and work your way up slowly. This stimulates not only the lymph but also the circulation.
• Have a professional masseur perform manual lymphatic drainage, especially in case of swelling or water retention. This massage technique moves fluid in the lymphatic channels toward the heart and promotes decongestion.
• After training or in the morning, alternate showers with cold and warm water. Start with warm and finish with cold water to stimulate circulation and lymph flow. Water walking, knee showers and warm full baths also stimulate the lymphatic system.
• Use diuretic medicinal herbs. These include nettle, dandelion, birch leaves, horsetail and horse chestnut. They support the removal of stalled lymph.
• Dilute oils such as lemon, cypress or juniper in a carrier oil (e.g. jojoba oil) and massage gently into the skin. You can also use the oils in a diffuser to create a lymph-stimulating atmosphere.
• Elevate your legs at night and use special venous pillows to reduce congestion.
• Avoid direct sun exposure, as vessels dilate in hot weather and lymph is more likely to pool in tissues. 
• For venous weakness, compression stockings are recommended to help prevent fluid retention. However, consult a doctor first.

The lymphatic system is an essential part of our body that protects us from disease and removes waste products. By caring for this system we promote our health and overall well‑being.