How can I tell if my toddler's rash is poison ivy?

If your toddler has swollen, red patches of skin on his face, arms, or legs, there's a chance it's poison ivy, poison oak, or poison sumac – especially if he's been playing in an area where one of those plants may be growing.

The rash, known as contact dermatitis, sometimes first appears in streaks or lines where the skin touched the poisonous plant. It usually shows up 12 to 48 hours after contact, though it can take up to a week to appear. Blisters follow and become crusty within a few days.

© Scott Camazine / Science Source

In the United States, poison ivy is most common in the Midwest and the East but can be found throughout the country except in the Southwest, Alaska, and Hawaii. Poison oak is most often found in the West and Southeast. Poison sumac prefers standing water, especially along the Mississippi River and in the eastern parts of the country.

Is the rash dangerous?

No, but it's very itchy. And because the rash can become infected, it's important to keep an eye on it.

Why do these plants cause rashes?

They contain a potent, irritating oil called urushiol. About 85 percent of the population is allergic to urushiol, making it the most common allergy in the country.

While no one's born with the allergy, exposure to the plant produces sensitivity to it. In other words, your body responds only after repeated exposure. So your toddler may brush against the plant several times without problem, only to break out in a rash the next time he meets up with it.

The oil's contained in the sap of the plant's leaves, stems, and roots, and it takes only one-billionth of a gram of urushiol to cause a reaction. Most cases show up in the spring and summer, when sap's plentiful and the plants bruise easily, but it's possible to get poison ivy, oak, or sumac any time of year.

How did my toddler get poison ivy?

Your toddler either touched the plant oil or something with the oil on it – for example, a ball, a gardening tool, or a pet that had come in contact with the plant.

How should I treat the rash?

Poison plant rash has no cure. You just have to let it run its course, which takes 14 to 20 days. In the meantime, try some of the following remedies to help relieve the itch and prevent infection:

Soothe your toddler's skin with cool compresses or a cool bath with a little baking soda, Epsom salts, or oatmeal (use a colloidal oatmeal bath treatment, sold at most drugstores).

Rub the affected area gently with an ice cube for ten to 20 minutes several times a day.

Blot your toddler's skin with cotton balls soaked in calamine lotion or a paste of baking soda and water three or four times a day. Don't use any lotions, creams, or sprays that contain antihistamines, though, as these can trigger allergic reactions.

Should I call the doctor?

It's a good idea to call your toddler's doctor about a rash, especially if you aren't sure what caused it. If you know the culprit was poison ivy, oak, or sumac and decide not to call right away, keep an eye on it and phone if:

the rash is severe or looks infected (you see pus or increasing redness)

the rash is on your toddler's face or genitals

your child runs a fever

the rash lasts longer than two weeks

If your toddler's rash is severe, his doctor may give him an oral antihistamine or oral steroids to stop the inflammation and help relieve the itching.

Is it contagious?

No, your toddler can get the rash only from touching something with the oil on it. And the liquid in the blisters doesn't contain urushiol, so the rash can't be spread by scratching or popping them.

If you notice a new patch of rash on your child a few days after the first one appears, it's not because the rash has spread. It's because the irritation can take longer to show up on certain parts of the body (areas with thicker skin take longer to absorb the urushiol). New rashes can crop up, though, if your toddler continues to be exposed to the oil, which can linger under his fingernails, on clothing, or on a pet's fur.

Is there any way to prevent the rash?

The only way to prevent it is to avoid making contact with the plant and its sap. But that can be tough, as the plants aren't always easy to recognize.

The old axiom is "Leaves of three, let it be." And while poison ivy and poison oak do tend to have three-leaf clusters, poison ivy can have as many as nine leaves per cluster, poison oak can have up to five, and poison sumac usually has seven to 13 small leaves.

The plants can take the form of bushes or vines and grow in the woods, near the water, and even in the backyard. Sometimes they wind around other plants, making them even harder to spot.

If your toddler's going to be playing outdoors near bushes or shrubs or hiking in the woods with you, dress him in long pants, socks, and a long-sleeved shirt. You might also try an over-the-counter barrier ointment to protect his skin against contact with the plant oil. This ointment is rubbed on the skin, much like sunscreen. It can be rubbed off, though, so don't assume it provides complete protection.

As soon as you return home from an outing in an area that may have poisonous plants, change your toddler's clothes, and always wash them before putting them on him again.

What should I do if I think my child's been exposed but he doesn't have a rash yet?

If you think your toddler's been exposed to poison ivy, oak, or sumac, immediately rinse the area with cool running water – a lot of it. If you use too little water, or even a small amount of soap and water, you may just spread the oil on the skin. So rinse his skin thoroughly to eliminate the oil.

The sooner you do this the better — within five minutes is best, but within 30 minutes will help. Then give your toddler a bath with soap and water.

Wash your toddler's clothes and toys and even the family pet if they've been exposed to the plant oil. (Wear rubber gloves when washing things by hand, and then throw away the gloves.)

What happens if my toddler breathes urushiol in the air?

If plants containing the oil are burned, it's possible for the smoke to carry the irritating substance. In that case, the poisoned smoke irritates the airway and lungs, but it doesn't affect the skin. (Firefighters working in forests thick with poison oak or ivy sometimes develop serious lung irritation from inhaling urushiol.)

It's extremely unlikely your toddler will accidentally breathe air that contains urushiol, but if you think he has, take him to the doctor. And if you find poison ivy, oak, or sumac in your yard, don't burn it.