Hives, also known as urticaria, are skin reactions characterized by raised, itchy welts that can appear anywhere on the body, varying in size and shape. While many cases of hives are temporary, some individuals experience chronic hives, defined as recurring welts for six weeks or longer. There is a recognized connection between chronic hives and thyroid disease, particularly autoimmune conditions affecting the thyroid gland.
Understanding Hives
These welts are red or skin-colored bumps that can range from the size of a pinhead to larger than a dinner plate and may join together to form larger patches. A defining characteristic of hives is that when pressed, the center of a red hive turns white, a process called “blanching.” The bumps can appear, disappear, and reappear rapidly, often within hours, and may change shape or location. While individual welts usually last less than 24 hours, new ones can continue to emerge.
The Link Between Thyroid Conditions and Hives
A significant association exists between chronic hives and autoimmune thyroid diseases. Autoimmune conditions, where the immune system mistakenly attacks the body’s own tissues, are linked to a notable percentage of chronic hive cases. Hashimoto’s thyroiditis, a common autoimmune thyroid disease leading to an underactive thyroid, is frequently observed in individuals with chronic hives. Graves’ disease, which causes an overactive thyroid, also shows an association, though Hashimoto’s is more prevalent among those with chronic hives. Research indicates that chronic spontaneous urticaria is associated with autoimmune thyroid disease in a range of 4.3% to 57.4% of adult cases.
The underlying mechanism involves the immune system’s dysregulation. In autoimmune thyroid conditions, the immune system produces autoantibodies that target the thyroid gland. These autoantibodies, such as anti-thyroid peroxidase (TPOAb) and anti-thyroglobulin (TgAb), are found more frequently in people with chronic hives compared to the general population. It is thought that this heightened immune activity, initially directed at the thyroid, can create a generalized inflammatory state in the body. This inflammation can lower the activation threshold of mast cells in the skin, causing them to release histamine and other chemicals more readily, leading to hives.
Another theory suggests that thyroid and skin cells might share certain proteins, leading to a cross-reactive immune response where autoantibodies bind to mast cells in the skin, prompting histamine release. Elevated levels of certain immune chemicals, like interleukin-6 (IL-6), and an imbalance in regulatory T cells are observed in both chronic hives and autoimmune thyroid diseases, indicating shared pathways. This immune system overactivity can manifest as chronic hives even when thyroid hormone levels are within the normal range, as the immune system’s attack on the thyroid can spill over to the skin.
Diagnosis and Management of Thyroid-Related Hives
Identifying a connection between chronic hives and thyroid disease involves a thorough medical evaluation. Healthcare professionals often begin by taking a detailed medical history and conducting a physical examination. If a link to thyroid issues is suspected, specific diagnostic tests are typically ordered.
These tests include thyroid function tests, such as Thyroid-Stimulating Hormone (TSH), Free T3, and Free T4, to assess thyroid hormone levels. Additionally, thyroid antibody tests, specifically for anti-thyroid peroxidase (TPOAb) and anti-thyroglobulin (TgAb), are important to detect the presence of autoimmune thyroid disease. The presence of these antibodies indicates an underlying autoimmune process.
Managing hives linked to thyroid conditions often involves addressing the underlying thyroid disorder. For individuals with an underactive thyroid due to Hashimoto’s, treatment with levothyroxine, a synthetic thyroid hormone, may not only manage the thyroid condition but also help relieve hives. Some studies suggest that normalizing thyroid hormone levels can lead to an improvement in hive symptoms. However, not all patients with thyroid autoimmunity will experience hive resolution solely from thyroid treatment, and some may require additional therapies for hive control.
For symptomatic relief of hives, antihistamines are a common first-line treatment. Second-generation non-sedating antihistamines like cetirizine, loratadine, and fexofenadine are often recommended. In cases where these are insufficient, higher doses or alternative antihistamines may be prescribed. Other treatments, such as omalizumab or immunosuppressants, might be considered for severe or persistent cases that do not respond to antihistamines. While these medications manage hive symptoms, addressing the underlying thyroid autoimmunity remains a key aspect of comprehensive care when a connection is established.