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Poison Oak Rash

What is a Poison Oak Rash?

Poison oak rash is a skin reaction that occurs after contact with poison oak plant. The rash usually appears within 8 to 48 hours after initial contact with the plant or may also take about 5 to 15 days to show up after direct contact with the plant. The onset of rash for those who comes into contact with the plant for the first time usually takes a week or longer. Later contacts with poison oak usually take a day or two before the rash develops.

Poison oak is among the poison plant that contains irritant that can trigger an allergic reaction to human upon contact. It is the counterpart of poison ivy and is a deciduous shrub that is native to North America and widespread in the valleys and mountains of California. The poison oak plant grows as a vine with roots that are rather aerial and is attached to the trunk of an oak tree and sycamore trees. It is inhabited in shady canyons and riparian and readily regenerates after it have been disturbed, such as in fire and land clearing.

It is important to identify the poison oak so as to avoid touching or coming into contact with it. Poison oak composed of three leaflets that are clumped together and botanically identified as one leaf. The color of the leaves is usually reddish bronze during the spring then turns green in new leaves as the spring season progresses. The fruits of poison oak are called drupes and just about the size of a pea. It has a green tint and smooth then the outer skin falls off upon maturity similar to a peeled orange fruit. Only the female poison oak plant will produce fruit continuously while the male plant is for pollination only.

How Does a Poison Oak Rash Look Like?

Allergic contact dermatitis is the type of rash displayed after contact with poison oak plant. This allergic contact dermatitis is an inflammation of the skin that is itchy and is non-contagious and non-life threatening although the development of the rash can be very uncomfortable for the affected individual.

The rash in poison oak is like a skin lesion or an elevated bump with reddish color. The bumps or red patches resemble a burn and the bumps are severely itchy. The rash may also ooze and for some time the rash becomes dry and crusty and may become raw and thickened or scaled. The area surrounding the rash will also swell and with skin redness and becomes more tender and warmer to touch. Pain in the affected site may also be perceived. The skin of the affected site may darken in color and later becomes leathery or cracked if the rash is left untreated.

Symptoms of Poison Oak Rash

The onset of rash in poison oak usually takes 8 to 48 hours from exposure to the plant or may take 5 hours to 15 days for those who were exposed for the first time. Onset of rash from repeated exposure usually takes much quicker which is about a day or two of exposure.

The general symptoms of poison oak rash include the following:

  • The area of the skin that comes in contact with the plant becomes itchy
  • General redness or red streak appears on the site that encountered the plant or any of its parts
  • The appearance of small bumps that are reddish in color
  • Fluid filled bump oozes out
  • Pain and tenderness over the affected site can be perceived

The symptoms of allergic contact dermatitis in poison oak may continue for a month before it can completely resolve. The symptoms will also recur if another contact with the same allergen ensues.


The poison oak and its other counterpart contain a chemical that causes an allergic reaction once in contact. Urushiol is an irritating and soapy sap contained in the poison oak plant. It is a toxic substance contained in the sap of poison oak and is a mixture of phenolic compounds known as catechols, potent benzene ring compound with carbon atoms of long side chain of 15 to 17.

Urushiol is found in resin canals of the plant only and not in the pollen and is also not on the surface of the leaves and stems unless these are bruised on chewed on by some insects. The toxic sap emitted in the freshly cut stem is described as sticky and black shiny lacquer similar to a pruning sealer. The sap is produced in the resin canals of the stem, leaves, roots, flowers and leaves. The resin canals in cross section reveal tiny black dots found the phloem layer located just inside the bark. Resin canals can also be found in the waxy mesocarp of the fruit beneath its skin.

The urushiol is the allergen itself that can cause the rash in an individual that comes into contact with it. The toxic substance can be transmitted through direct contact with the plant such as in the case of firemen battling forest fires are potentially at risk for poison oak rash when they brush on the plants during the process of fire control.

Direct handling of the plant predisposed an individual to rash especially if the plant has bruises or cuts that can emit the toxic sap. Urushiol can also be transmitted through indirect contact such as handling tools, equipment and other objects that comes in contact with the poison oak.

Poison Oak Rash Pictures

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Most rashes from poison oak including its counterpart can be managed and treated successfully at home. It is advisable to wash the affected site with water immediately after exposure to remove the sap attached to the skin.

The treatment of poison rash is directed towards the relief of symptoms and such include the following:

  • Wet compresses and cool baths are recommended to relieve the itchiness
  • Anti-itch cream and lotion application that contains anti-histamine and calamine will help to reduce and relieve the symptom of itchiness
  • In some cases, Corticosteroid cream, pills, ointments and injections may be prescribed to reduce the inflammation in moderate to severe cases of poison oak rash.

It is necessary to avoid scratching the rash as it can only aggravate and worsen the condition that might lead to other medical complications once infected when an open wound occurs from too much scratching. Smooth textured cotton clothing is also advisable to avoid irritating the rash even further.

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