OTCs Today
Daniel L. Krinsky, RPh, MS
With springtime fast approaching, certain “critters” will make their presence known via bites and stings. Insect bites and stings are common, and anyone who spends time outdoors is at risk. These usually cause only a local reaction, but they can produce a mild allergic reaction or life-threatening anaphylaxis in patients who are sensitive to compounds in the insect’s saliva. Approximately 0.5% of the population may show signs of systemic allergic reactions to insect stings.
Bites from insects (e.g., mosquitoes, fleas, bedbugs) and from arachnids (e.g., ticks, chiggers) are nonvenomous. Each insect has distinctive biting organs and salivary secretions that contribute to the characteristic signs and symptoms of each type of bite.
A biting mosquito injects an anticoagulant saliva that causes the characteristic welt and itching. Mosquitoes serve as vectors for spreading serious systemic infections, including malaria and West Nile, Chikungunya, and Zika viruses. Approximately 20% of infected patients experience influenza-like symptoms with fever, fatigue, and possible joint pain.
Fleas are tiny bloodsucking insects that breed best in a humid climate. Humans are often bitten after moving into a vacant flea-infested habitat or when living with infested pets.
Bedbugs usually hide and deposit their eggs in crevices of walls, floors, picture frames, bedding, folds of linens, corners of suitcases, and furniture during the day; they bite their victims at night. The increased mobility of society worldwide has heightened concerns about an increased incidence of bedbug infestations in the United States in places frequented by travelers, such as hotels. Bites occur in clusters of twos and threes and usually in a straight line.
Ticks feed on the blood of humans and animals. Ticks should be removed intact within 36 hours of attachment using fine tweezers. Certain species of ticks can transmit systemic diseases such as Rocky Mountain spotted fever and Lyme disease. Early diagnosis and prompt treatment by a health care provider are essential to prevent development of serious manifestations.
Although all species of spiders are venomous, most are unable to penetrate the skin because their fangs are too short or too fragile. If a spider bite is suspected but cannot be confirmed, the patient should be monitored for symptoms such as pain, fever, chills, and joint pain.
Self-treatment options
Self-treatment objectives are to relieve swelling, pain, and itching; to prevent scratching that may lead to secondary bacterial infection; and to prevent future insect bites. Primary exclusions for self-treatment include signs of secondary infection and suspected spider bite requiring medical attention.
Nonpharmacologic management options include applying an ice pack or external analgesic to relieve pain and irritation. Nondrug measures to prevent insect bites include avoidance and use of repellents. Most commercial insect repellent products contain DEET. When applied, the volatile repellent releases vapors that tend to discourage the approach of insects. Before use, patients should review the EPA Guidelines for Safe Use of DEET.
External analgesics (local anesthetics), topical antihistamines, hydrocortisone, and some counterirritants are approved for treating pain and itching associated with insect bites. These agents are not approved for use in children younger than 2 years. Topical skin protectants reduce inflammation and promote healing. First-aid antiseptics and antibiotics can help prevent secondary infections. Systemic antihistamines often are used in treating itching, but this use is not a labeled indication.
Local anesthetics such as benzocaine, pramoxine, benzyl alcohol, lidocaine, and dibucaine are approved in topical preparations for relief of itching and irritation caused by insect bites. Pramoxine and benzyl alcohol have the safest profile. These cause a reversible blockade of conduction of nerve impulses at the application site, thereby producing loss of sensation. These products are generally applied to the bite area up to 3 to 4 times daily for no longer than 7 days.
Other agents that may offer benefit are hydrocortisone, topical antihistamines (primarily diphenhydramine), skin protectants, and counterirritants.
If symptoms worsen
Patients should follow up with a health care provider after 7 days of self-treatment. Advise patients to seek medical attention if symptoms such as redness, itching, and localized swelling worsen during treatment or if they develop secondary infection, fever, joint pain, or lymph node enlargement.