Poison ivy and poison oak rashes are caused by an allergy to the resin of these plants, called Rhus plants. You don’t have to come in direct contact with the leaves, roots, or branches of Rhus plants to get the rash. The plant resin can reach your skin indirectly when you touch clothing or a pet that carries the resin. Posion oak can spread through the air from the pollen.
Like other allergies, Rhus allergy is acquired; you’re not born with it. While some lucky people never become allergic to Rhus plants, most persons become sensitized at some time and remain allergic. Unfortunately, there’s no way to desensitize persons allergic to Rhus plants. These types of allergies are forms of allergic contact dermatitis.
Is poison ivy contagious?
Your poison ivy or poison oak rash is not contagious. The fluid in the blisters does not spread the rash.
Note that Rhus rash doesn’t appear immediately after exposure to the plant resin, but only after a time called the latent period. This latent period between exposure to the plant and appearance of the rash may be as short as four hours or as long as 10 days, depending on individual sensitivity and the amount of plant contact. Sometimes, more rash appears after treatment has begun. These new patches are areas that had a longer latent period.
Best treatment options
Rhus rashes are self-limited, i.e. sooner or later they clear up without treatment. Letting nature take its course with a mild Rhus rash is reasonable, but severe rashes need a visit to a doctor and treatment to ease the misery and disability they cause.
The best and safest treatment for Rhus rashes is wth a natural treatment such as Zanfel or with manganese sulfate solution. Manganese sulfate solution has been shown to be effective both to inactivate urushiol on the skin and to relieve itching.
Manganese sulfate solution probably acts as a chelating agent for detoxification of urushiol. Dr. West’s Poison Ivy, Oak, Sumac Cleanser is the most common manganese sulfate solution available for treatment of Rhus rashes.
Cortisone-type preparations taken by mouth are dramatically effective in treating Rhus rash. It’s safe in most people to take these drugs for a short period (2-3 weeks). If you have a peptic ulcer, high blood pressure, or diabetes, you should take cortisone only under close medical supervision.
Improvement of your rash should be prompt and steady. It depends on getting enough cortisone. If your rash doesn’t improve steadily, call your dermatologist to see what he or she recommends.
When the swelling has gone down, a cortisone-type preparation cream will help your rash heal. Do not use this until the swelling is down and blistering has stopped as it will not be effective.
You may bathe or shower as usual. Keep the water as cool as you can after the first shower (see below), and don’t use soap on your rash since it may irritate.
How can you prevent an outbreak?
The only way to prevent Rhus rash is to avoid contact with the plant resin. It’s traditional advice to wash with strong soap and warm water after exposure. This does no harm, but is only effective if you wash within 15 minutes of exposure. You will need to wash clothing, pets, and tools or you may become re-exposed to the resin.
Rhus plants may cause rashes throughout the year. Roots and stems can cause a rash just as much as the leaves. If you can’t recognize poison ivy or poison oak plants, have someone point them out so you can avoid them.