Dermatitis (aka Eczema) simply means "inflammation of the skin" with resulting transient or persistent itching, redness, scaling, rash.  
There are many types/conditions that cause dermatitis (the last two: AD & ACD - described below).
  • ICD (Irritant Contact Dermatitis) - ie: "dishpan hands," "chapped lips," or "diaper dermatitis."
  • Seborrheic Dermatitis - dandruff-like scaling of the scalp or skin patches on face/chest or "cradle cap" in infants.
  • Stasis Dermatitis, Neurodermatitis, Nummular Eczema, Dermatitis Herpetiformis, Viral Exanthems are related conditions.
  • AD (Atopic Dermatitis) - often worse in children, in those w/ genetic tendencies, sometimes worsened by ACD.
  • ACD (Allergic Contact Dermatitis) - due to contact allergens, the most classic being poison ivy/plant-oil dermatitis.

Atopic Dermatitis

Image by James Heilman, MD
Creative via Wikimedia Commons

AD (Atopic Dermatitis) is a very common, chronic, relapsing and very itchy skin disorder  - affecting over 10% of children.
ONSET: Most cases (90%) begin within the first 5 years of life, often slowly improving over the years.  Only 10% of AD first appears in adulthood (ie: without a childhood history of such).
DISTRIBUTION: The location of the lesions vary widely but "classic patterns" are as follows:  Infants - face, scalp, extensor surfaces (ie: wrists, knees, elbows) and on the lower buttocks.  Older children/adults - eyelids, hands, flexural folds (ie: inner wrists, elbow creases and space behind the knees).
NICKNAME: Eczema just means skin inflammation - however AD is the most common form of Eczema so the words are often used interchangeably.
FACTOID: They say that AD is "the itch that rashes."  In other words, affected skin itches like crazy due to the disease, but it doesn't rash until it is scratched.
CAUSE:   I like to think of it as "abnormal genetics" (ie: genes go awry so that there is a genetic tendency for immune cells to damage one's own skin).  The "tight junctions" are damaged between the top layer of skin cells (ie: keratinocytes) so that water can be lost easier and the skin becomes "dehydrated." 
ITCH/SCRATCH CYCLE: The dry skin itches terribly and scratching only worsens the micro-cracks leading even more water loss.  This continual itch/scratch cycle can lead to chronic thickening, scaling, "alligator skin" like damage.
COMPLICATIONS:  Bacteria, viruses, fungi/yeast usually can not penetrate into healthy skin.  However they can slip into micro-cracked damaged AD skin and colonize or infect the skin - causing the AD flare up even worse.

EXACERBATORS:  Irritants and allergens can also enter damaged skin easier -- resulting in AD flares or chronic lesions resistant to treatment.  Stress, heat, dry air, soap/detergent, frequent wetting/drying (ie: evaporation) and a host of other triggers can worsen AD.

COMORBIDITIES:  Stress can trigger AD.  Likewise, AD can cause chronic stress, leading to poor sleep, poor mood, poor school/work performance, increased anxiety, difficulty focusing, etc.  Asthma &/or Allergic Rhinitis is seen in about 50% of those with AD; however, many have no known contact, airborne or food allergies at all.

TREATMENT:  A Soak & Seal "Skin-Hydration" Regimen is Key (see handout).  Avoiding Irritants, Allergens, Stress and using Topical Medications and Antimicrobial Measures are also part of the care plan.

Allergic Contact Dermatitis

Image by Robert Stelzle, MD (at AABH)
Positive Patch Test: Allergen-Induced ACD Rash

ACD (Allergic Contact Dermatitis) is also very common itchy type of eczema.  

CAUSE: ACD is due to a "delayed" immunologic reaction to an allergen that penetrates into the skin.  Immune cells in the skin abnormally see "an allergen" linked to surface the affected skin cells as a foreign threat  - so they destroy the affected skin cells.  This leads to inflammation, swelling, itching and rash (aka - dermatitis).

MIMICKER:  ICD (Irritant Contact Dermatitis) is due to a physical things that damage the skin (ie: detergents, chemicals, solvents, alcohols, over washing and improper drying, temperature extremes, etc).  The Keratinocytes are damaged and the skin barrier becomes cracked, leading to less protection from future irritants - so the cycle can be hard to break.

ALLERGENS:  ACD, unlike ICD, is an actual delayed allergic (abnormal immune) reaction.  
  * Common allergens include: plant oils (ie: poison ivy, ragweed, tulip bulbs, pine/wood saps), Perfumes/Fragrances, Metals (ie: nickel, gold, cobalt...), Colophony (rosin), Rubber Chemicals, Plastic Resins, Dyes, Preservatives, and various Topical Medications (ie: neomycin, bacitracin, benzocaine, steroid or benadryl creams or ointments).  

PATCH TESTING: These chemicals can be placed on patches and left on the skin for 2-3 days and then read over the next several days to determine which, if any, is possibly causing ACD. 

Helpful ACD Related Websites: