What is serum sickness?

Serum Sickness
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Serum sickness

Serum sickness is an unusual reaction to any foreign substance in the body. Venom from insect stings or spider bites and medicines such as penicillin are common causes of this reaction.

Symptoms of serum sickness usually begin between 7 to 10 days after the person is exposed to the substance. A person usually feels generally unwell (malaise) and may have hives, joint pain, fever, headache, and swollen glands.

Having an episode of serum sickness puts a person at high risk for developing a severe allergic reaction if there is exposure to the same substance in the future. A person should avoid any medicine related to serum sickness after it has been identified. Venom immunotherapy may be an option to protect against insect or spider bites that caused the reaction.

How can you care for yourself when you have serum sickness?

  • Stop taking medicine that caused the sickness if your doctor tells you to. Don't take that kind of medicine again. Taking it even many years later can make you sick again. Your doctor may recommend a different medicine.
  • If you have a fever or joint pain, ask your doctor if you can take an over-the-counter pain medicine, such as acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve). Be safe with medicines. Read and follow all instructions on the label.
  • If you have a rash or hives, take a nondrowsy antihistamine, such as loratadine (Claritin). Be safe with medicines. Read and follow all instructions on the label.

Serum sickness: When to call

Call 911 anytime you think you may need emergency care. For example, call if:

  • You have severe trouble breathing.

Call your doctor now or seek immediate medical care if:

  • You have a rash in your mouth or on your genital area.
  • You have blisters on your body.
  • You have new symptoms, such as a cough or belly pain.
  • Your joint pain gets worse.
  • You have new or worse trouble breathing.

Watch closely for changes in your health, and be sure to contact your doctor if:

  • You have a new or higher fever.
  • You do not get better as expected.

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