Contact Dermatitis

Two mechanisms, two timelines - Allergic contact dermatitis is type IV and peaks 48 to 72 hours after exposure; it will not drop a pressure on induction. Contact urticaria is the immediate wheal-and-flare, and while most cases are mild it can progress to anaphylaxis. Work out which one the chart is actually describing before you build a plan around it.

Chlorhexidine is the one that can kill - Chlorhexidine can produce wheezing, rash, facial swelling, and anaphylactic shock, and it should not be used at all in anyone with a documented chlorhexidine allergy. The catch is that it is not only in the prep: it sits in impregnated line dressings, coated catheters and tubes, and oral rinses, so "we didn't prep with it" does not mean it wasn't given. Anaphylaxis to it has been reported in anesthetized patients where the trigger was only identified on later workup.

Have the alternative prep decided in advance - If chlorhexidine is out, the options are povidone-iodine, chloroxylenol, isopropyl alcohol, and benzalkonium chloride. Povidone-iodine is itself off the table in known iodine or ingredient allergy, and benzalkonium causes little irritant dermatitis but has weaker antimicrobial coverage. Settle this with the surgeon before the patient is on the table, not after the prep is open.

Adhesives, electrodes, and the tape line - Rubber gloves are a common cause of chronic allergic contact dermatitis, and acrylics and preservatives are recognized contact allergens; contact dermatitis to a BIS sensor has been reported, as has allergic contact dermatitis to a dye or alcohol in a chlorhexidine-based skin preparation. If the history mentions a rash under a dressing, ECG pad, or wristband, use silicone or hypoallergenic securement, site electrodes on unaffected skin, and write down where you put everything.

Nickel is the most common allergen - Across more than 44,000 patch-tested patients, nickel sensitivity averaged 17.5%, and pooled contact allergy prevalence sits near 20% with nickel leading. It turns up in jewelry, everyday metal items, and medical devices. Have jewelry and piercings off before the patient comes back.

Latex sits in both boxes - Latex causes type I IgE-mediated reactions, and the chemical antioxidants added during processing cause type IV reactions as well. Latex allergy is among the most common causes of anaphylaxis in the operating room. A patient who reports only a rash from gloves is not thereby cleared for a latex-containing room. See the Latex Allergy entry.

Broken barrier is an infection problem - Disrupted skin loses the body's most important barrier and raises the risk of secondary bacterial infection. Don't site an IV, arterial line, epidural, or block through actively inflamed skin. Pick intact skin, and if there isn't any, carry that infection risk explicitly into the plan and the note.

If it isn't dermatitis, it's an emergency - Hypotension, bronchospasm, or airway swelling with a "contact reaction" is anaphylaxis: remove the allergen, protect the airway, give epinephrine early, and resuscitate with fluid. See the Anaphylaxis entry.

Treatment when it flares - Removing the offending agent is the crucial step. Topical corticosteroids are first-line when under 20% of the body is involved and oral corticosteroids when more; topical calcineurin inhibitors such as tacrolimus or pimecrolimus suit delicate areas, and hydroxyzine or cetirizine control the itch. Keep high-potency topical steroids off thin skin - face, genitals, intertriginous areas - because of atrophy.

Get the allergen named properly - Patch testing is the gold standard for identifying the responsible agent and screens metals, rubber, formaldehyde, lanolin, fragrances, preservatives, and medicines. Refer for patch testing rather than leaving "reacts to tape" in the chart; the next anesthesia provider needs the name of the chemical, not the symptom.

It is also an occupational disease - Contact dermatitis prevalence has been studied among surgical assistants, anesthesia assistants, and anesthesiologists, and glove-related hand dermatitis is a documented cause. Your own hands count.

Contact dermatitis is inflammatory eczematous skin disease caused by something that touched the skin, and it splits into two mechanisms that behave very differently in the OR. Irritant contact dermatitis is direct chemical damage: keratinocytes release proinflammatory cytokines, the barrier breaks down, there is no immune memory, and enough exposure will do it to anyone. Allergic contact dermatitis is a type IV delayed hypersensitivity, where a hapten under 500 daltons crosses the stratum corneum, Langerhans cells carry it to draining nodes and sensitize T cells, and on re-exposure those T cells drive inflammation peaking 48 to 72 hours later. That delay is why allergic contact dermatitis almost never presents as an intraoperative crisis, and why an immediate wheal-and-flare after a prep or a glove is a different problem entirely.