Allergies and swollen lymph nodes can both be unpleasant, but the two are generally not related. An allergy occurs when your immune system erroneously overreacts to a harmless substance. An allergy-triggering substance is called an allergen. Lymph nodes are part of your immune system and contain cells that fight infections, not allergens. Therefore, allergies typically do not cause lymph node swelling. However, airborne allergies sometimes lead to infectious complications that may be accompanied by swollen lymph nodes. Additionally, other medical conditions can develop unrelated to existing allergies and lead to lymph node swelling.
Immune Response to Allergens
An allergy develops when the immune system mistakenly identifies a harmless allergen, like pollen, as harmful. Initial exposure to the allergen stimulates production of allergen-specific antibodies called immunoglobulin E (IgE). These antibodies attach to immune cells called mast cells, which populate tissues like the skin and the lining of the nose, lung, stomach and intestines.
Once allergen-specific IgE antibodies form, subsequent exposure to that allergen stimulates mast cell activation, with release of histamine and inflammatory chemicals called cytokines. These chemicals trigger allergy-related symptoms like a runny nose, itchy eyes and throat, sneezing and wheezing.
Immune Response to Infections
Like mast cells, lymphocytes are immune cells with specialized functions. They fight infectious invaders like bacteria and viruses. Lymph nodes are encapsulated collections of lymphocytes found in clusters in various locations throughout the body. When an infection occurs, lymph nodes near the site of the infection may temporarily swell due to lymphocyte activation. In contrast, lymphocytes are not activated during an allergic reaction.
Swollen Lymph Nodes Related to Allergy Complications
Although allergies typically do not cause lymph node swelling, infectious complications of airborne allergies can cause swollen glands. For example, sinus and middle ear infections sometimes develop in people battling airborne allergies due to pollen, pet dander, mold or another allergen. These infections can cause swollen and tender lymph nodes in the head and neck area. The enlarged lymph nodes return to normal size once the infection clears.
Swollen Lymph Nodes Unrelated to Allergies
Many illnesses can cause swollen lymph nodes. Some conditions, like a head cold, might be confused with allergies due to similar symptoms. Other illnesses can occur coincidentally in a person already experiencing allergies and lead to lymph node swelling. Common infections that may coexist with allergies and cause swollen lymph nodes in the head and neck include: -- Upper respiratory tract infection. -- Throat infection. -- Pink eye. -- Infectious mononucleosis.
Less common causes of swollen lymph nodes in the head and neck region that are unrelated to airborne allergies but can occur along with them include: -- Infections, such as HIV, syphilis and cat scratch disease. -- Cancer, such as leukemia, lymphoma, and head and neck cancer. -- Autoimmune conditions, such as lupus and sarcoidosis.
Warnings and Precautions
It is common to experience a swollen lymph node in your head and neck area. Most are due to infections and typically go away when the underlying cause resolves. However, enlarged lymph nodes sometime signal a serious medical condition. Seek medical evaluation for widespread lymph node enlargement, or one or more swollen lymph nodes with any of the following characteristics: -- Firm, hard consistency. -- Enlargement for longer than 6 weeks. -- Rapid growth. -- Size greater than three-quarters of an inch.
Also seek medical attention as soon as possible if you may have recently been exposed to HIV or experience lymph node swelling accompanied by any warning signs and symptoms, including: -- Unexplained fevers or night sweats. -- Unintentional weight loss. -- Persistent cough. -- Breast lumps. -- Difficulty breathing or swallowing.
Reviewed by: Tina M. St. John, M.D.