How to tell if you have a poison oak rash and how to treat it

• A poison oak rash looks like red, swollen bumps that may blister over.
• It often appears in a streaky pattern, since many people unknowingly brush up against the plant.
• To treat a poison oak rash, use a steroid cream, calamine lotion, or antihistamine.

Poison oak is a shrub that grows on the US west coast and can cause an allergic skin reaction in about 85% of Americans. Touching the plant results in an itchy, painful rash that may take a couple of weeks to fade.

Here's what you need to know about monitoring the symptoms of your poison oak rash and how to treat the itching and discomfort.

What are the symptoms of a poison oak rash?

A poison oak rash tends to appear about a week or two after you're first exposed, says Steven Feldman, MD, a dermatologist at Wake Forest Baptist Health.

At the site of contact, it can cause symptoms like:

• Itchiness
• Swelling
• Redness
• Blisters

These rashes often appear in a streaky pattern that indicates someone has brushed up against the plant, says Feldman.

It doesn't matter what part of the poison oak plant you touch. The leaves, stem, and roots all contain urushiol, which is the oil that triggers skin irritation and causes a rash.

If you are exposed to urushiol - either by touching poison oak directly or something that's come into contact with the plant, like clothing -, "you'll probably have the rash for 2 weeks - basically until the outer layer of the skin goes through the natural shedding process," Feldman says.

Note: Poison oak rashes tend to be more severe and quicker to appear if you've gotten the rash before. "If you are highly allergic to it from previous exposure, the rash may appear in a few days," says Feldman.

Treatment for poison oak

Here are a few remedies you can try to help calm any itching and discomfort.

1. Use a steroid cream or medication

An anti-inflammatory steroid cream, like hydrocortisone, can help reduce symptoms like itching, redness, and swelling, says Feldman.

If your rash is severe and over-the-counter creams aren't working, your doctor can prescribe a stronger cortisone cream or an oral steroid like prednisone, Feldman says.

2. Try calamine lotion

Calamine lotion creates a cooling sensation when it evaporates, which can offer relief from itching. If you have blisters on your rash, it can also help dry up any leaking fluid.

3. Take an antihistamine

When you touch poison oak, your body releases histamines - messenger cells that trigger symptoms like swelling and itching.

Antihistamines - as the name implies - are medications that block your immune cells from reacting to histamines. These medications don't always work for poison plant rashes, but they can help reduce itching when used with other treatments like hydrocortisone, Feldman says.

When to see a doctor

You may need to see a doctor immediately to treat a poison oak rash if:

• You get poison oak on sensitive areas of your body like your eyes, mouth, or genitals.
• You have any signs of infection, including:
• New red streaks appearing on your skin
• Pus or yellow scabs on your rash
• A fever over 100 degrees Fahrenheit

• Your symptoms seem to be getting worse after seven to ten days of the rash appearing.

You should also see a doctor "if it is so severe that you cannot stand the itching," Feldman says.

Insider's takeaway

For most people, poison oak causes an itchy and uncomfortable rash that can last at least a week.

There are several home remedies you can try to ease your symptoms, like taking antihistamines or using ointments on your skin.

However, if your rash is severe, isn't getting better with treatment, or looks like it's infected, you should get medical attention as soon as possible.