A 35-year-old man with a history of asthma presented with an exposure after spraying his garage with an insecticide he bought at the hardware store. Shortly after spraying the insecticide, he noticed eye itchiness, tingling, pruritus over his arms and legs, and shortness of breath. His blood pressure was 130/85 mm Hg, heart rate 70 bpm, respiratory rate 14 bpm, temperature 98.7°F, and SpO2 96% on room air.
He was alert and anxious, his skin was warm with mild erythema, and he had urticaria over his forearms and ankles. His lung exam revealed diffuse wheezing bilaterally. His eyes were watery, and his pupils were 4 mm and reactive bilaterally. The remainder of his exam was unremarkable.
-Carbamates and organophosphates may be found in products used in households, gardens, and farms. They are also found in powders, sprays, and shampoos targeting fleas and ticks in animals.
-Organochlorines including hexachlorocyclohexane (Lindane) are historically used in products such as DDT, chlordane, aldrin, and toxaphene that are now generally banned in most countries.
-Pyrethrins and pyrethroids include cypermethrin, imiprothrin, and tetramethrin that can be found in household Raid products. Permethrin is also in this class, and is used in Nix and Elimite to kill head lice and scabies.
-Boric acid is found in ant and roach killers.
-Pet-related products used as topical insecticides to kill fleas on cats and dogs include neonicotinoid imidacloprid (Advantage), GABA receptor antagonist fipronil (Frontline), GABA-releasing agents avermectin and ivermectin (Revolution), and selamectin (Revolution).
Toxicities of Insecticides
Carbamates and organophosphates inhibit acetylcholinesterase. Toxicity is manifested as muscarinic signs (SLUDGE, bradycardia, miosis) and nicotinic signs (muscle fasciculations, tremors, weakness).
Organochlorines are absorbed by the skin due to their lipophilic properties. They may cause CNS stimulation and seizures. Mechanisms of toxicity for the different classes of organochlorines include sodium channel opening and GABA antagonism.
Pyrethrins/pyrethroids are derived from chrysanthemums and typically have low toxicity in humans. Toxicity in insects is attributed to its sodium channel-opening properties. Pyrethrins may cause allergic reactions in humans. Pyrethroid type I "T" syndrome includes tremors, and a pyrethroid type II "CS" syndrome includes choreoathetosis, salivation, paresthesias, nausea, vomiting, diarrhea, pulmonary symptoms, and neuroexcitation. Additional toxicity from exposure to pyrethroid-containing products may be from other ingredients such as solvents and surfactants. Boric acid is associated with blue-green emesis and a "boiled lobster" rash.
Management of Pyrethrin/Pyrethroid Insecticide Exposure
Identification of ingredients can be found by looking at the available Safety Data Sheets (SDSs) or Material Safety Data Sheet (MSDS). Removal from the source of exposure and dermal decontamination should be initiated.
Patients with an anaphylactic should be treated like patients with any other anaphylactic reaction, using diphenhydramine, antihistamines, epinephrine, and intubation as required. Treat asthma exacerbations or wheezing with nebulized beta agonists and steroids. Decontaminate any areas that have been exposed to the insecticide using copious amounts of water. Vitamin E has been used to treat paresthesias anecdotally. Irrigate the eyes and do a fluorescein check to evaluate for any corneal involvement. Refer to an ophthalmologist for corneal injury.
The patient had been using a pyrethroid-based insecticide. He was monitored and given Benadryl, prednisone, and nebulized albuterol. His skin and eyes were copiously irrigated. His eyes had no evidence of corneal injury on Wood's lamp examination, and improved after irrigation. He was monitored for six hours in the emergency department, and his symptoms resolved. He was discharged and advised to open the garage to allow any residual insecticide to dissipate.