Irritant contact dermatitis
|Irritant contact dermatitis|
|Classification and external resources|
Irritant contact dermatitis is a form of contact dermatitis that can be divided into forms caused by chemical irritants and those caused by physical irritants.
Chemical irritant contact dermatitis 
Chemical irritant contact dermatitis is either acute or chronic, which is usually associated with strong and weak irritants respectively (HSE MS24). The following definition is provided by Mathias and Maibach (1978): The mechanism of action varies between toxins. Detergents, surfactants, extremes of pH, and organic solvents all have the common effect of directly affecting the barrier properties of the epidermis. These effects include removing fat emulsion, defatting of dermal lipids, inflicting cellular damage on the epithelium, and increasing the transepidermal water loss by damaging the horny layer water-binding mechanisms and damaging the DNA, which causes the layer to thin. Strong concentrations of irritants cause an acute effect, but this is not as common as the accumulative, chronic effect of irritants whose deleterious effects build up with subsequent doses (ESCD 2006).
Common chemical irritants implicated include solvents (alcohol, xylene, turpentine, esters, acetone, ketones, and others); metalworking fluids (neat oils, water-based metalworking fluids with surfactants); latex; kerosene; ethylene oxide; surfactants in topical medications and cosmetics (sodium lauryl sulfate); alkalies (drain cleaners, strong soap with lye residues).
Physical irritant contact dermatitis 
Physical irritant contact dermatitis is a less researched form of ICD (Maurice-Jones et al.) due to its various mechanisms of action and a lack of a test for its diagnosis. A complete patient history combined with negative allergic patch testing is usually necessary to reach a correct diagnosis. The simplest form of PICD results from prolonged rubbing, although the diversity of implicated irritants is far wider. Examples include paper friction, fiberglass, and scratchy clothing.
Low humidity 
In a recent analysis of patient data, low humidity from air conditioning was found to be the most common cause of PICD (Morris-Jones, Rachael et al.)  To the lay person a definition of low humidity being a physical irritant can be confusing because low humidity is a deficit (or absence) of an elemental substance, whereas ALL other irritants implicated in contact dermatitis are in concentrations of relative abundance. So the irritant is actually a lack of another substance, namely water vapour. This confusion is further compounded with the use of the term contact implying 'touching' (as is the case with all other forms of PICD) whereas in the case of low humidity PICD there is an absence of contact with water vapour.
Many plants cause ICD by directly irritating the skin. Some plants act through their spines or irritant hairs. Some plant such as the buttercup, spurge, and daisy act by chemical means. The sap of these plants contains a number of alkaloids, glycosides, saponins, anthraquinones, and (in the case of plant bulbs) irritant calcium oxalate crystals - all of which can cause CICD (Mantle and Lennard, 2001).
Butternut squash and Acorn squash have been known to cause an allergic reaction in many individuals, especially in food preparation where the squash skin is cut and exposed to the epidermis. Food handlers and kitchen workers should take precautions to wear rubber or latex gloves when peeling butternut and acorn squash to avoid temporary Butternut squash (Cucurbita moschata) dermatitis A contact dermatitis reaction to butternut or acorn squash may result in orange and cracked skin, a sensation of "tightness", "roughness" or "rawness". Applying Cortisone cream to the affected area should stop the reaction within 24 hours.
- HSE Guidance Notes. Guidance Note MS 24 - Health Surveillance of occupational skin disease. http://www.hse.gov.uk/pubns/ms24.pdf
- Mathias CG, Maibach HI (1978). "Dermatotoxicology monographs I. Cutaneous irritation: factors influencing the response to irritants". Clin. Toxicol. 13 (3): 333–46. doi:10.3109/15563657808988241. PMID 369770.
- Morris-Jones R, Robertson SJ, Ross JS, White IR, McFadden JP, Rycroft RJ (2002). "Dermatitis caused by physical irritants". Br. J. Dermatol. 147 (2): 270–5. doi:10.1046/j.1365-2133.2002.04852.x. PMID 12174098.
- Mantle D, Lennard TWJ. Plants and the skin. Brit J Derm Nurs. 2001 (Summer).