Hyperthyroidism may present with an itchy rash, hives, or changes in skin pigmentation. Medications that treat hyperthyroidism may also cause a rash.

Hyperthyroidism, also known as overactive thyroid, is a condition in which your thyroid gland makes too many hormones. As thyroid hormones affect nearly every major organ in your body, hyperthyroidism can affect almost every organ, including your skin.

An excess of thyroid hormones causes your body functions to speed up. This can lead to increased blood flow, metabolic rate, and cell growth, which can all affect your skin.

Whether you’ve recently received a hyperthyroidism diagnosis and are undergoing treatment, or if you’re suddenly experiencing unusual skin changes, here’s what you need to know about the possible ways an overactive thyroid gland can affect your skin health.

Hyperthyroidism may cause skin cells to grow rapidly in number. Unlike hypothyroidism, which may cause dry and pale skin, hyperthyroidism is linked to the following skin issues:

  • Skin rash: This most often develops in the creases of your skin.
  • Hives: Also called urticaria, hives consist of painless, raised patches of skin that may also itch.
  • Itchiness: This may occur with or without rashes or hives.
  • Skin discoloration: The affected areas may also feel waxy and hard.
  • Unusual warmth: An increased metabolic rate can cause heat sensitivity, which may cause warm, sweaty skin.

The most common cause of hyperthyroidism is Graves’ disease. With Graves’ disease, you may also develop pretibial myxedema, which causes lumpy and inflamed skin on your lower legs. Also called Graves’ dermopathy, this skin condition often occurs along with eye bulging and swollen fingers.

Depending on your skin tone, a hyperthyroid rash may appear red, purple, or brown. You may also have hives, which show up as raised patches.

A hyperthyroid rash may be itchy and painful. The skin around your rash may be warm to the touch, and you may experience sweating from sensitivity to heat.

It’s also possible to experience redness and sweating in the palms of your hands and soles of your feet, as well as a face flushing.

Other signs include thinning skin and hair.

Other symptoms of hyperthyroidism

A rash on its own isn’t likely to indicate hyperthyroidism. Consider talking with a doctor if your rash accompanies any of these other symptoms:

  • rapid heart rate
  • insomnia
  • fatigue
  • nervousness
  • irritability
  • hand tremors
  • increased appetite with unintentional weight loss
  • increased thirst
  • muscle weakness
  • heat intolerance
  • increased urination and bowel movements
  • diarrhea
  • decreased libido
  • bulging in one or both eyes

Sometimes hyperthyroidism can also cause an enlargement of the thyroid gland, which can cause swelling in the front of your neck. This is called a goiter.

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With hyperthyroidism, your metabolism and other major body functions speed up, which can cause rashes.

If you already have this thyroid condition, you may be able to help reduce the onset of a hyperthyroid rash by avoiding triggers. This includes a high iodine intake from medications, supplements, and foods like kelp. Avoiding nicotine may also help.

According to a 2021 case report, researchers also believe there is a link between autoimmune thyroid diseases, such as Graves’ disease, and the development of hives.

In some cases, hyperthyroid treatments may also cause a rash. An itchy rash may indicate that your antithyroid medications are affecting your liver function.

Skin conditions and overactive thyroid

Though not direct causes on their own, having some preexisting skin conditions may increase your risk of developing hyperthyroidism. These include:

Treating hyperthyroidism may improve rashes and other skin problems. Depending on the severity of your condition, this may involve:

In addition to hyperthyroid treatments, a doctor may prescribe other short-term therapies to target related skin problems directly. These may include:

Consider talking with a doctor about possible signs of hyperthyroidism, including skin rashes. They will likely order blood tests that can check your thyroid hormone levels to determine whether you have an overactive thyroid gland.

Also, contact a doctor right away if you develop a sudden rash or hives that are quickly progressing or if you have other symptoms such as breathing difficulties, fever, or drainage. These may be signs of a more serious condition.

Are rashes an early symptom of hyperthyroidism?

You’re more likely to experience other hyperthyroidism symptoms first, like a rapid heart rate or fatigue.

Where does hyperthyroid rash appear?

A hyperthyroid rash can show up anywhere on your body. According to the American Academy of Dermatology, they may be more common in the creases of your skin. With Graves’ disease, you may also see them more often on your lower leg and feet.

How can I prevent a hyperthyroid rash?

Following your treatment plan may help reduce the risk of developing a hyperthyroid rash. You can also try to avoid possible triggers, such as iodine and nicotine.

An excess of thyroid hormones in your body causes hyperthyroidism and its resulting symptoms. These can include rashes that may itch and hurt.

With treatment and regular monitoring, a doctor can help you reduce your thyroid hormone levels. Over time, this can help reduce rashes and other skin problems.