Rhus Dermatitis

Aka: Rhus Dermatitis, Poison Ivy, Poison Ivy Dermatitis, Poison Oak, Poison Sumac, Toxicodendron radicans, Rhus toxicodendron, Urushiol

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II. Epidemiology

  1. Prevalence of complete Rhus Immunity: 10-15%
  2. Prevalence Rhus Allergy: Total of 75-85% of U.S. Adults
    1. Consistent Reaction: 50% of U.S. Adults
    2. Reaction to high doses: 25-35% of U.S. Adults

III. Pathophysiology

  1. Allergic Contact Dermatitis to Rhus Group of Plants
    1. Poison Oak (West of the Rocky Mountains)
    2. Poison Ivy (East of the Rocky Mountains)
    3. Poison Sumac (Swampy areas in Florida, Northeast)
  2. Hypersensitivity Reaction to Urushiol oil
    1. Sensitivity to one plant confers sensitivity to all
    2. Oil leaks out from damaged plant
    3. Oil evaporates from skin within 4 hours
    4. Oil evaporates much more slowly from fomites (years in some cases)
      1. Garments
      2. Animal hair (cat, dog)
      3. Ash in smoke from burning leaves
  3. Recurrent Eruption is not related to Vesicle leakage
    1. Vesicles have sterile (non Rhus) content
    2. Repeat eruption is related to re-inoculation
    3. See description of slower oil evaporation above

IV. Symptoms

  1. Very pruritic rash

V. Signs

  1. Papulovesicular Dermatitis
    1. Linear formation (associated with Rhus oil spread)
  2. Inhalational reaction may also occur
    1. Burned Poison Ivy leaves (e.g. brush clearing) can result in significant airway inflammation

VI. Differential Diagnosis

  1. Irritant Contact Dermatitis
  2. Allergic Contact Dermatitis
  3. Viral Exanthem
  4. Impetigo (superinfected excoriations)
  5. Photocontact Dermatitis
    1. Contrast with Rhus airborne Contact Dermatitis
    2. Does not affect some airborne Rhus areas
      1. Retroauricular folds
      2. Submental folds
      3. Nasolabial folds

VII. Management

  1. Symptomatic Treatment (sooth and dry weeping lesions)
    1. Cool compresses for 15-20 minutes per hour
    2. Topicals
      1. Colloidal Oatmeal Bath (Aveeno bath)
      2. Calamine lotion applied several times per day
      3. Burow's Solution (Topical astringent, e.g. Domeboro)
      4. Topical Analgesics (e.g. Menthol, camphor)
        1. Avoid Topical Anesthetics (e.g. topical Diphenhydramine, topical Lidocaine or benzocaine)
    3. Antihistamines tend to offer minimal relief
      1. Atarax at bedtime for Pruritus may help with sleep and sedation
      2. Oral Antihistamines fail to offer benefit as Histamines are not central to Rhus Dermatitis related Pruritus
      3. Do NOT use topical Antihistamines (skin sensitizers)
  2. Corticosteroid
    1. Topical Corticosteroids (for Mild to Moderate Localized Involvement)
      1. Strong Topical Corticosteroids (e.g. Clobetasol or Temovate gel, soothing if refrigerated)
      2. Avoid Hydrocortisone and other inadequately weak Topical Corticosteroids
      3. Most effective prior to Vesicle formation
      4. Use ointment for very dry lesions
    2. Systemic Corticosteroids (for severe cases)
      1. Indications
        1. Severe, Widespread involvement (esp. >20% of body)
        2. Sensitive region involvement (e.g. periorbital or genital lesions)
      2. Avoid short courses (e.g. Medrol dose pack) due to rebound worsening
        1. Curtis (2014) J Clin Med Res 6(6):429-34 +PMID:25247016 [PubMed]
      3. Adults
        1. Start: Prednisone 60 mg orally per day divided doses
        2. Taper: Decrease by 10 mg every third day x18 days
      4. Children
        1. Start: Prednisone 0.5 - 1 mg/kg/day to 40-60 mg/day
        2. Taper by 5 mg every three days over 18 days
    3. Supersensitive patient early in recurrence (<12 hour)
      1. Triamcinolone 40-60 mg IM or
      2. Combination
        1. Betamethasone 12 mg IM (short acting) AND
        2. Methylprednisolone 40 mg IM (long acting)
  3. Antibiotics
    1. Indicated for signs of superinfection
    2. Mild: Topical Antibiotics
    3. Severe: Oral Antibiotics

VIII. Course

  1. Mild, delayed reaction in 90% patients
    1. Pruritic papulovesicular lesions form over 1-2 days
    2. Resolves over 10 to 14 days
  2. Severe reaction in 10% of patients
    1. Onset of debilitating rash over 4 to 8 hours

IX. Prevention

  1. Washing off oil immediately (within 10 minutes) may prevent rash
    1. Soap and Water (preferred)
      1. Scrub for several minutes to remove oils
    2. Solvents poured over area
      1. No evidence for higher efficacy than cheap and effective soap and water
      2. Products
        1. Tecnu Outdoor Skin Cleanser (or Zanfel)
        2. Other non-specific solvents
          1. Acetone
          2. Rubbing Alcohol (Isopropyl Alcohol)
          3. Anecdotally Gasoline has been used, but causes significant Burn Injury and is NOT recommended
      3. Do not dab on solvent (e.g. Alcohol pad, towelettes)
        1. Spreads Rhus oil
      4. Use Solvents only when ready to travel home
        1. Removes lipid protective skin coating
        2. Can predispose to worse second Rhus exposure
  2. Clean all contaminated clothing, shoes, and linens
    1. Urushiol oil can remain on unwashed items for years
    2. Launder washables
    3. Use Solvents above for non-washables
  3. Consider Ivy Block (e.g. Ivy X Pre-Contact) applied to skin prior to exposure
    1. Variable efficacy and not typically recommended (unproven efficacy)
  4. Wash pets
  5. Identify plants to avoid
  6. Wear protective clothing when hiking in weed areas

X. References

  1. (2013) Presc Lett 20(8): 46
  2. (2023) Presc Lett 30(6): 33
  3. Baer (1990) Cutis 46:34-6 [PubMed]
  4. Gayer (1988) Cutis 42:99-100 [PubMed]
  5. Epstein (1991) J Wilderness Med 2:183-6 [PubMed]

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Related Studies

Ontology: urushiol (C0077941)

Concepts Hazardous or Poisonous Substance (T131) , Organic Chemical (T109)
MSH C003747
SnomedCT 17685003
English urushiol, Urushiol, Urushiol (substance)
Spanish urushiol (sustancia), urushiol
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Poison Ivy Dermatitis (C0162451)

Concepts Disease or Syndrome (T047)
MSH D011040
SnomedCT 5205006, 200823002
English Dermatitides, Poison Ivy, Poison Ivy Dermatitides, Poison Ivy Dermatitis, Contact dermat.:poison-ivy, DERMATITIS POIS IVY, POIS IVY DERMATITIS, poison ivy dermatitis, dermatitis due to contact with poison ivy, contact dermatitis due to poison ivy (diagnosis), contact dermatitis due to poison ivy, Poison ivy rash, dermatitis ivy poison, ivy poison, Poisoning;ivy, ivy poison rash, rash poison ivy, poison ivy rash, poison ivi, Ivy poison, poison ivy, Allergic dermatitis due to Rhus toxicodendron, Allergic dermatitis due to poison ivy, Contact dermatitis due to Rhus toxicodendron, Contact dermatitis due to poison ivy, Contact dermatitis due to poison-ivy, Contact dermatitis due to poison ivy (disorder), Contact dermatitis due to poison-ivy (disorder), Dermatitis, Poison Ivy, Dermatitis due to poison ivy, Dermatitis due to Rhus toxicodendron, ivy poisoning
Dutch giftige klimop rash, klimop; gif, Gifsumacdermatitis
French Eruption provoquée par le sumac vénéneux, Dermatite due au sumac vénéneux
German Poison ivy-Ausschlag, Poison-Ivy-Dermatitis, Giftsumach-Dermatitis
Italian Eruzione da edera velenosa, Dermatite da edera velenosa
Portuguese Exantema por hera venenosa, Dermatite por Hera Venenosa
Spanish Erupción por hiedra venenosa, dermatitis alérgica por Rhus toxicodendron, dermatitis de contacto por Rhus toxicodendron, dermatitis de contacto por Rhus toxicodendron (trastorno), dermatitis alérgica por hiedra venenosa, dermatitis de contacto por hiedra venenosa (trastorno), dermatitis de contacto por hiedra venenosa, dermatitis por contacto con hiedra venenosa, Dermatitis por Hiedra Venenosa
Japanese ツタうるしかぶれ, ﾂﾀｳﾙｼｶﾌﾞﾚ
Czech Exantém způsobený jedem břečťanu, jedovatec kořenující - dermatitida, dermatitida vyvolaná škumpou jedovatou, škumpa jedovatá - dermatitida, dermatitida vyvolaná jedovatcem kořenujícím
Hungarian Mérges szömörce okozta kiütés
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Poison Sumac (C0330962)

Concepts Plant (T002)
MSH D012251
SnomedCT 261311000, 65317008
English Poison sumach, Sumacs, Poison, Poison Sumacs, sumac poison, poison sumac, Poison Sumac, Sumac, Poison, Poison sumach (organism), Poison elder, Poison sumac, Rhus venenata, Rhus vernix, Toxicodendron vernix, Toxicodendron vernix (organism), Toxicodendron vernix (L.) Kuntze, poison ash
Spanish Fustete Venenoso, Zumaque Venenoso, zumaque venenoso, zumaque venenoso (organismo), Toxicodendron vernix (organismo), Toxicodendron vernix
German Giftsumach, Sumach, Gift-
French Poison sumac, Toxicodendron vernix, Sumac à vernis
Portuguese Sumagre-Venenoso
Dutch Gifsumak, Sumak, gif-
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Poison Oak (C0446292)

Concepts Plant (T002)
MSH D012251
SnomedCT 261309009
Portuguese Toxicodendro Venenoso Oriental Verdadeiro, Toxicodentro Venenoso Ocidental Verdadeiro
Spanish Roble Venenoso, roble venenoso (organismo), roble venenoso
German Gifteiche, Eiche, Gift-
French Toxicodendron diversilobum, Chêne poison, Sumac vénéneux à feuilles de chêne
English Oaks, Poison, Poison Oaks, oak poison, poison oak, oaks poison, Oak, Poison, Poison Oak, Poison oak, Poison oak (organism)
Norwegian Gifteik
Dutch 'Poison oak'
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Rhus toxicodendron (C0937645)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D012251
English Rhus Toxicodendron, Rhus toxicodendron, toxicodendrons, Rhus, Rhus toxicodendrons, toxicodendron, Rhus
French Rhus toxicodendron
Norwegian Toxicodendron radicans, Rhus toxicodendron
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Poison Ivy, Oak and Sumac (C1456686)

Definition (MEDLINEPLUS)

If you spend time outdoors, chances are you have been bothered by poison ivy, poison oak or poison sumac at some point. Most people are sensitive to the plants' oily sap. The sap is in the root, stems, leaves and fruit of these plants. If it gets on your skin, it causes a blistering skin rash. The rash can range from mild to severe, depending on how much sap gets on your skin and how sensitive you are to it. Problems can also happen if the plants are burned. Airborne sap-coated soot can get into the eyes, nose, throat and respiratory system.

The best way to avoid the rash is to learn what the plants look like and stay away from them. If you come into contact with the plants, wash your skin and clothing right away. If you develop a rash, ask your pharmacist about over-the-counter medicines. For severe rashes, see your doctor.

National Park Service
Concepts Injury or Poisoning (T037)
English Poison Ivy, Oak and Sumac
Derived from the NIH UMLS (Unified Medical Language System)

Related Topics in Dermatology

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