Arthus Reaction

What is arthus reaction?

Arthus reaction is a hard, painful, swollen area that can happen under your skin where you’ve received a booster vaccination. It’s most common with diphtheria and tetanus vaccinations (which are combined in a Tdap shot), but can happen with any shot that you’ve received multiple doses of.

Arthus reaction is a type III hypersensitivity response. Hypersensitivity responses happen when your immune system overreacts or incorrectly responds to something foreign — like pollen or germs — entering your body. Arthus reaction is usually something that can happen when you’re injected with a booster dose of a vaccine — an additional dose of a previous vaccine. But some people also consider farmer’s lung (a type of hypersensitivity pneumonitis) and other localized type III hypersensitivities to be arthus reactions. Bug bites could also potentially cause an arthus reaction.

What are the symptoms of arthus reaction?

Symptoms of arthus reaction happen around the area where you got an injection, within four to 12 hours of vaccination. Symptoms include:

• A hard, very painful lump.
• Swelling.
• Redness or discoloration.
• Open sore or ulcer.

What causes arthus reaction?

Arthus reaction happens when your body reacts to an additional dose of a vaccine by sending cells and fluid to the injection site.

Your immune system recognizes things it encounters in your body as “self” or “non-self” by attaching to (binding) markers called antigens. When your immune system first sees an antigen it doesn’t recognize, it can create antibodies that are designed to bind to the antigen and alert other immune system cells to attack it. Your immune system then remembers that antigen so it can attack the antigen more quickly the next time it sees it.

Vaccines use different methods to get your body to recognize an antigen without making you sick. The next time your body sees that antigen after you’ve been vaccinated against it, it can fight it off quickly. When you’re injected with a booster of a vaccine, the IgG antibodies you made during the original vaccination can activate immune cells at the injection site. This causes your blood vessels to open up, filling the area with fluid and immune cells.

This buildup of fluid and cells causes a lump and swelling under your skin — arthus reaction. Sometimes, immune complexes (antibodies bound to antigens) cause vasculitis by sticking to the insides of your blood vessels. When this happens, blood might not be able to flow through, causing tissue to die from lack of oxygen.

What are the complications of arthus reaction?

Rarely, arthus reaction can cause your tissue to die (necrosis). If left untreated, this can lead to wound infection.

How is arthus reaction diagnosed?

Healthcare providers diagnose arthus reaction by learning about your symptoms and examining the injection site. They may test tissue or fluid around the reaction or do blood tests to help make a diagnosis.

How is arthus reaction treated?

Arthus reactions usually go away on their own and don’t need treatment. If the reaction is severe or lasts more than a few days, your provider might treat you with:

• Corticosteroids to reduce inflammation.
• Pain relievers to keep you comfortable.
• Antihistamines to block some of the chemicals causing the reaction.
• Icing the area to decrease swelling.

If you have complications like necrosis, a provider may surgically remove dead tissue (debridement) or prescribe antibiotics to treat or prevent infections.

Can arthus reaction be prevented?

You can prevent arthus reaction by avoiding the cause. If you’ve been diagnosed with arthus reaction to a diphtheria or tetanus vaccine, your provider might suggest you go longer between boosters than is typically recommended. It’s important not to skip scheduled vaccinations without consulting a healthcare provider.

How long does arthus reaction last?

Arthus reaction usually goes away on its own in a few days. If your reaction is severe or lasts a long time, you may need treatment to get better or to prevent complications.

When should I see my healthcare provider?

See a healthcare provider if you develop a hard, painful lump after getting a vaccine or being bitten by a bug, or if you have a wound that’s not healing. They can diagnose the issue and determine what kind of treatment (if any) is best.

When should I go to the ER?

Go to the nearest emergency room or seek emergency medical care if you have swelling or a wound that’s:

• Very painful.
• Blistering.
• Foul-smelling.
• Black.
• Warm to the touch.
• Oozing gray or white fluid.

What questions should I ask my doctor?

You may want to ask your provider:

• Is this an arthus reaction or an expected vaccine side effect?
• When can I expect it to get better?
• How can I take care of myself at home?
• Is there any way to prevent this in the future?
• When should I follow up with you?

How common is arthus reaction to vaccines?

Arthus reaction to vaccines is extremely rare. Only 1 in 10 million people report having this kind of reaction.

What’s the difference between arthus reaction and serum sickness?

Arthus reaction and serum sickness affect your body differently and happen under different circumstances. Arthus reaction happens only at the site of a vaccine injection. Serum sickness causes inflammation in your entire body. It can happen with treatments like monoclonal antibodies (a concentrated fluid, or serum, that contains antibodies that help you fight an infection) when your immune system mistakenly attacks the serum.

A note from Cleveland Clinic

Arthus reaction is a rare and painful condition you can get after receiving certain vaccinations. But most often, it goes away on its own without causing any lasting effects. Talk to a healthcare provider if you think you’re experiencing arthus reaction. They can let you know what serious symptoms to look out for and how to avoid it in the future.