Poison Ivy

What is Poison Ivy?

Poison ivy, Toxicodendron radicans, is a native plant that is covered with a poison oil called urushiol. If it comes into contact with your skin, either by brushing up against it or through secondary contact from your boots or your dog, it causes an allergic reaction characterized by a painful, red, itchy rash that forms bumps and blisters that can start to ooze.

Around 85% of the population is allergic to poison ivy. Some people are highly allergic, and even secondary contact can cause a severe rash. Others are not allergic at all, but it is important to remember that increased contact with the plant will also increase sensitivity to it, so it’s best that everyone avoids this plant!

How does it cause a rash?

The resinous oil urushiol penetrates the skin and binds to proteins in your skin cells within minutes and stops them from communicating with other cells, causing an auto-immune reaction. Your own immune system is tricked into attacking your skin cells!

You can develop a rash within 4-48 hours depending on how allergic you are. If you have never had poison ivy before, it may take 1-3 weeks for your immune system to recognize the oil. Time is of the essence if you have come into contact with the plant, and washing the area as soon as possible with cool or lukewarm soap and water for at least 30 seconds is necessary.

I didn’t touch any plants, why do I have a rash?

Urushiol is extremely stable and can live on a surface 10+ years, with specimens several centuries old still causing rashes upon contact. If you think you have come into contact with poison ivy, it is important to put clothing directly in the wash when you get home. This is also good advice for ticks. You may wipe your boots, gear, tools, and skin down with rubbing alcohol or a poison ivy post exposure wipe before showering with cool or lukewarm water and using dawn dish soap or a specialized soap like tecnu for 30 seconds on the exposed area.

Hot water makes your skin more vulnerable to the oil, and a bath will cause the oil to float to the surface and make contact with other parts of your skin. If you are extremely allergic, you can shower with tecnu extreme as a body wash.

If you choose to wipe your skin down with rubbing alcohol, this will also strip your protective skin barrier. Use multiple wipes to avoid just spreading the oil around. It is important that you do not re-expose your skin after this step as you can make yourself more vulnerable to urushiol.

What not to do?

Do not use hot water, do not take a bath, do not break blisters on a developed rash, do not use bleach to treat the rash. Do not scratch the rash. This can cause broken skin and infection, scars, and it will take a longer time to heal. Blisters caused by the rash are filled with clear blood plasma fluid, not more urushiol oil as is commonly thought. Do not apply rubbing alcohol to an active rash as this will cause skin irritation. Do not apply topical antihistamines to an active rash as this can make it worse.

How to protect yourself from Poison Ivy

Wear long pants, long sleeves, closed-toed shoes, and learn how to spot the plant and steer clear of it. Do not mow, weed whack, or burn the plant. Stay on trail & do not touch any plants you can’t identify!

How to identify it?

Poison Ivy is a shapeshifter and has a high morphological and structural diversity, in addition to being able to grow nearly anywhere. Its characteristics can change in different environments and habitats. While the leaf margins (edges) can feature a few irregular, jagged notches, teeth, or mitten-like lobes, they will primarily remain smooth.

Berries of white, take flight!

If you see a hairy rope, don’t be a dope.

Leaves of three, let it be.

Longer middle stem, stay away from them.

Red leaflets in spring, it’s a dangerous thing.

How can I treat it?

Are you sure that your rash is from poison ivy? Urushiol rashes are nearly always extremely itchy. They also appear often in a straight line from brushing up against vegetation. If the rash is not in a straight line, it may be from a secondary exposure, like from petting your dog who has been running through vegetation.

Anything you can do to keep the rash dry and oil-free will help. Make sure that the oil is entirely gone from your skin with specialized soap like Tecnu or Zanfel. As long as the oil is entirely absent, taking a hot shower can relieve some symptoms of the rash. Cold compresses can relieve any swelling, and calamine lotion or other over the counter anti-itch creams can help.

Seek emergency medical attention if:

You have inhaled smoke from burning poison ivy. Inhaling the smoke is very dangerous and can even lead to death.
Your face is swelling, or if the rash affects your eyes, mouth, or genitals.
You develop a fever >100F.
The rash doesn’t get better in a few weeks.

Poison Ivy is beneficial??!!

It is sometimes humans first instinct to kill or eradicate anything that can pose a threat to us or that we don’t understand. Instead of understanding it and learning to value it, we just want to get rid of it right away.

Poison ivy is an early successional native plant that contributes to the food web. It produces nutritious white berries that birds love to eat and are a critical food source in winter. It is a generalist plant that grows well in disturbed areas or edge habitat where other plants might struggle to establish, shading the ground. The robust root system stabilizes the soil and stops erosion - which benefits the water quality of Fresh Pond.

Only humans and some primates are allergic to poison ivy – no other animal or bird. Deer, muskrats, rabbits, horses, birds, and insects can eat the leaves and berries. Read a full list of all the wildlife that rely on poison ivy here.

There are many ecological benefits to this native plant. If poison ivy didn’t cause an uncomfortable rash, humans might plant it purposefully as groundcover!

Why is it at Fresh Pond Reservation & What is the Cambridge Water Department doing about it?

Unfortunately, here at Fresh Pond it can be found growing in many spots along the perimeter fence and also along the edges of wooded areas. Although we remove as much as we can each year, (and as a result, its prevalence has been reduced) it does continue to be a problem.

As a water supply with off-leash dogs, management options are limited

No synthetic herbicides (water supply water quality concerns)
No goats (off-leash dogs)
Tried a weed-steamer used on organic farms but found it too loud, too big (takes up most of the pond road), too smelly (burns hydrocarbons), and has a small water tank that would need refilling in areas with no access to water
Organic salt spray “A.D.I.O.S.” has been tried, but not very effective

Manual control is our most effective option

Every winter, landscape maintenance contractors circumnavigate the pond and manually cut back all the poison ivy stems off the perimeter road fence line. Staff also seek out large stalks in wooded areas growing up trees to cut and minimize its spread.

Recently, we have gone even further by hiring landscape maintenance crews to carefully cut back poison ivy from pathways and fence lines during the growing season while the leaves are active. Don't do this at home, kids!

For more information contact Amanda Garms, Ranger at (617) 349-6489 or fpr@cambridgema.gov

Signage

References

https://tecnu.com/

https://poison-ivy.org/

https://www.mayoclinic.org/diseases-conditions/poison-ivy/symptoms-causes/syc-20376485

https://www.si.edu/stories/poison-ivy-primer

https://www.cdc.gov/niosh/docs/2010-118/pdfs/2010-118.pdf

http://aad.org/public/everyday-care/itchy-skin/poison-ivy/rash-appear

https://www.poison.org/articles/poison-ivy-oak-and-sumac