Insect Bite

INTRODUCTION Insect bites or stings result in the introduction of venom or toxins into the skin, which in turn cause the release of vasoactive amines. This results in marked swelling and erythema of the thin tissues of the eyelid. Unless secondary infection occurs, these reactions tend to resolve rapidly. Dermatitis nodosa is a specific type of insult due to barbed cilia acquired from caterpillar contact. The barbs result in the cilia working their way into the skin where they set up a prolonged, sometimes severe inflammatory irritation. If the caterpillar hairs get into the eye, they cause a severe, painful reaction and can lead to later ocular sequelae from intractable inflammation (ophthalmia nodosa).

CLINICAL PRESENTATION Insect insults result in localized eyelid inflammation with redness and swelling.

Pain and pruritis can be intense. A minute skin defect at the site of insult may be present. Abscess formation may result due to secondary infection, localized tissue necrosis, or as a reaction to retained stinger or mouthpart. Severe hypersensitivity reactions with hemorrhagic bullae, chills, and fever several hours after the sting or bite may be seen. In rare cases an insect bite can lead to cellulitis and even necrotizing fasciitis. Rarely a toxic shock like syndrome can result with vomiting, fever, and circulatory collapse. Bee stings to the eye have been reported to result in demyelinating optic neuritis and blepharochalasis with recurrent episodes of eyelid edema. Dermatitis nodosa presents as one or more localized inflamed and tender nodules.

The Bite Mosquitoes The Eyelid
(Courtesy of Robert A. Goldberg, M.D.) (Courtesy of Charles S. Soparkar, M.D.)

HISTOPATHOLOGY The histopathological reaction to insect bites differs widely, as would be expected by the varied clinical responses. The usual reaction to an arthropod bite, such as from a mosquito, is a mixed inflammatory infiltrate containing lymphocytes, macrophages, eosinophils, and sometimes neutrophils. Variable degrees of spongiosis and dermal edema also are present. The histopathological findings in insect bites are non-specific and require clinical-pathological correlation.

Arthropod Bites Histopath

DIFFERENTIAL DIAGNOSIS An insect bite or sting may mimic preseptal cellulitis, chalazion, orbital cellulitis, or allergic or contact dermatitis, a localized abscess nodule or ruptured inclusion cyst.

TREATMENT If any part of the insect is left at the site of attack it should be carefully removed. Although cold compresses are usually recommended some types of venom are actually deactivated by heat. In severe cases antihistamines are sometimes useful in minimizing the reaction. Systemic anaphy-laxis developing in sensitized individuals requires prompt recognition and treatment. Recent observations indicate that Dapsone (4,4'-diaminodiphenlysulfone) can be useful in reducing severe necrotizing inflammation, such as that occurring after brown recluse spider bits, and thereby reduce subsequent scarring and deformity. Antipruritics, analgesics, and in select cases steroids may be needed.

REFERENCES

Allington HV, Allington RR. Insect bites. JAMA 1954; 155:240-247.

Barnard JH. Cutaneous responses to insects, types, and mechanism of reactions. JAMA 1966; 196:159-162. Duke-Elder S. System of Ophthalmology, Vol. 13. St. Louis: Mosby, 1974:201.

Fan PC, Chang HN. Hypersensitivity to mosquito bite: a case report. Gaoxiong Yi Xue Ke Za Zhi 1995; 11:420-424. Finney JL, Peterson HD. Blepharochalasis after a bee sting. Plast Reconstr Surg 1984; 73:830-832. Poitelea C, Wearne MJ. Periocular necrotizing fasciitis—a case report. Orbit 2005; 24:215-217.

Song HS, Wray SH. Bee sting optic neuritis. A case report with visual evoked potentials. J Clin Neuroophthalmol 1991; 11:45-49.

Thakur CP. The syndrome of ptosis, generalized muscular weakness and marked fasciculations of calf muscles due to insect bite. J Indian Med Assoc 1965; 45:503-504.

How To Reduce Acne Scarring

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