Poison oak rash – pictures and how to treat it

Poison Oak: Home remedies for the rash and how to recognize it

Most people are familiar with poison ivy which produces a substance called Urushiol which is oily and sticky and adheres to virtually anything it touches.  The oil can be absorbed into the skin and produces a rash that can variously sting, itch, or irritate. But there are numerous other plants outdoors that should you make physical contact with, will make you potentially very unwell. Toxicodendron diversilobum, commonly known as “Pacific poison oak” or “western poison oak“, is a woody vine originating from the sumac family of plants, “Anacardiaceae” (source).

It is widely found in western North America, inhabiting conifer and mixed broadleaf forests, woodlands, grasslands, and chaparral biomes. Peak flowering occurs in May. Here’s what it looks like:

poison oak

Image source: Oregonstate.edu

Image Source: https://edis.ifas.ufl.edu/ep220

How quickly does the rash develop?

If you come into contact with poison oak, a rash can take three or four days to develop and it gets more itchy as time progresses.  As it increases, bumps and lumps under the skin will start to form and eventually create large blisters which will ooze and weep.  After a few days, the blisters will dry up and become crusty.  The serum from the blisters will not spread and make the rash worse and the rash itself is not contagious.

Not everyone will have a bad reaction but some people can have a very severe response which may require prompt medical intervention.

Serious allergic reactions to poison oak

A serious allergic reaction is when the body overreacts to an allergen and this is called anaphylactic shock or anaphylaxis.  This can present with one or more of the following symptoms:-

  • Difficulty breathing
  • Swelling in the throat which makes swallowing difficult and uncomfortable
  • Facial swelling
  • A rash which covers 25% or more of your body
  • Fever
  • Headache
  • Nausea
  • Signs that the blisters have become infected

Any of these symptoms require immediate medical investigation.

How to identify the rash?

Some people are not aware that they have come into contact with poison oak until a rash appears.  So how can you identify it?

The rash most commonly appears on the wrists, ankles, and neck where the skin is thinner and will better absorb the Urushiol.  It often takes about a week to make itself known and sometimes this can be traced back to a particular gardening episode or a period of time spent out walking.

rash from the poison oak

Image source: Medicalnewstoday.com

How long does the rash last?

Usually from the point of its appearance, the rash will last about a week to ten days although in some cases, it can last longer, so up to a month.

Treatment with home remedies

For most people, unless they experience a severe allergic reaction, the rash will run its course and is uncomfortable but not serious.  It can be treated symptomatically with home remedies much as you would treat any other form of dermatitis or skin itching and irritation.  The rash can be very itchy and scratching will only make it worse and could cause a skin infection.  The itching develops after a few days and can be very persistent so it is important to manage it otherwise the temptation to scratch it is just too great, particularly for children.  Here are some ways to manage the itching until the rash clears up:-

  • Initially, wash thoroughly with warm soapy water; the oil sticks to everything and it can have inadvertently spread to other parts of your body you are not aware of and which won’t be apparent as the rash does not develop immediately. If you have touched the poison oak with your hands then pay extra attention to your fingers and fingernails
  • Once the rash is present then cool baths with either a cup of oatmeal or two cups of Epsom salts can help soothe the skin
  • Apply aloe vera gel after the bath to affected areas or Calamine lotion
  • Cool compresses can offer topical relief during the day
  • Apply chilled cucumber slices to areas of rash on your arms
  • There are lots of topical cooling lotions and creams – the type of thing used for sunburn – some are clay-based and these can all help soothe and calm the inflammation and irritation
  • Wear loose cotton clothing rather than tight weave or harsh fabrics which will heat the skin and are not breathable causing you to sweat which will definitely increase the irritation and itchiness
  • Antihistamines, like diphenhydramine, can ease the itchiness. A range of antihistamines is available for purchase over the counter or from Amazon.com

Always make sure you wash your clothing if you can identify the point at which you can into contact with the plant.  Urushiol can remain on clothes almost indefinitely and will cause a second rash if you touch it again.  If the rash is very severe and uncomfortable then your doctor may prescribe antihistamines by mouth to dampen down the reaction.  These can take a couple of days to work so symptomatic relief is still important.

Prevention is always better than cure

If you don’t know what poison oak looks like but think you may have it in your garden then learn to identify it.  It is a leafy shrub although it can grow up to six feet tall. It can look rather like a climbing vine and is not dissimilar to poison ivy but is actually more shrub-like with leaves shaped like the leaves from an oak tree.  The leaves are red or green in spring with the plant then producing small flowers that are white, yellow or green.  In summer, the leaves are green and the plant grows berries.  In late summer and early fall, the leaves turn orange and red.  Make sure you’ve taken a look at pictures online before you head out walking, particularly if you’re hiking a new trail or you’re unfamiliar with that area.

Keep yourself covered up completely if you are exposed to the plant.  You can pick up traces of Urushiol from any part of poison oak, not just the leaves.  It is also still a problem when the plant is dead so a rash will develop if you touch it.  If you remove the plant and burn it, then the resultant smoke can be very toxic and dangerous and cause severe respiratory problems if you inhale it.

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