Approach To Bites And Stings Insect Stings Local Reactions

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Almost all hymenoptera stings will result in a local reaction, which includes redness, swelling, pain, and itching at the site of the injury. These reactions tend to occur almost immediately and last for a few hours. The local tissue response is a consequence of a histaminelike reaction caused by the venom that is released by the sting. Local reactions can be treated with ice and antihistamine for itching. Tetanus prophylaxis should be provided for those who have not been vaccinated.

Delayed Reactions

Large local reactions are immunoglobulin (Ig) E-mediated allergic reactions to the hymenoptera venom. These reactions are often confused with cellulitis. as large areas (>1() cm in diameter) of redness and warmth develop over 24-48 hours. These reactions are not infectious and will not respond to antibiotics. These reactions are best treated with oral steroids initiated early after the sting. Tetanus prophylaxis should be reviewed and updated, if needed. A person with a history of a large local reaction to a bee sting is likely to have similar reactions to subsequent stings. However, the history of this type of reaction does not result in an increased risk of anaphylaxis to subsequent stings.


Up to 4% of the population may have a systemic reaction to a hymenoptera sting. Those who have had a systemic reaction have a 50% or greater risk of having a systemic reaction to future slings. These systemic reactions can vary from milder symptoms of nausea, generalized urticaria, or angioedema to severe and life-threatening hypotension, shock, and airway edema. Severe immediate-hypersensitivity reactions usually occur within minutes of the sting.

Treatment of anaphylaxis should include assessment and management of the ABCs (Airway. Breathing, and Circulation), with intubation, if necessary, IV access, and fluid resuscitation. Subcutaneous or intramuscular injection of 0.3-0.5 mL of 1:1000 solution of epinephrine should be given as quickly as possible and repeated in 10-15 minutes if needed. Antihistamines and bron-chodilators may be required as well. Anyone with iui anaphylactic reaction should be observed in a hospital setting for 12-24 hours, as the symptoms can recur. Persons with known anaphylactic reactions should be prescribed epinephrine injector kits to carry with them for immediate access at all times when they could be exposed. Desensitization therapy can also be offered to those with known anaphylaxis, as their risk of future severe reactions can be reduced by up to 50%.

Animal Bites

Nearly 5 million animal bites occur in the United States each year. The most common animals involved are dogs, cats, and humans.

The initial management should focus, as always, on the ABCs and on protection of the current injury (splinting of fractures, protection of cervical spine, etc.), as well as control of bleeding and assessment of the injuries incurred. History should be gathered on the type of animal involved in the bite, the situation regarding the bite (whether provoked or unprovoked), and the vaccination status of the animal, particularly to document rabies vaccination status.

Local cleaning of the wound(s) with soap and water, irrigation with saline, and debridement of devitalized tissue should take place as soon as possible. Often, for minor wounds, these treatments are all that is needed.

The risk of infection is dependent on numerous factors. Larger and deeper wounds are more likely to become infected than smaller, superficial wounds. Hand wounds also tend to have an increased risk of infection. Host factors, such as the presence of chronic illnesses or immune suppression, also play a role. The animal involved in the bite is important. Approximately 20% of dog-bite wounds become infected, whereas cat and human bites have a higher occurrence of infection.

Many different bacteria can be involved in bite wound infections. Both cats and dogs can carry staphylococci, streptococci, anaerobic species, and Pasteurella species. Humans carry staphylococci, streptococci. Haemophilus species, Eikenella species, and anaerobes.

The treatment of bite wounds starts with local care—cleaning, irrigation, and debridement. The primary closure of bite wounds is controversial, but obviously infected wounds should not be primarily closed. Tetanus vaccination should be updated in those patients at need. Animal control authorities should be contacted for guidance regarding rabies vaccination.

Patients with moderate to severe wounds from dog, cat, or human bites, who are seen early after the injury and without signs of active infection, should receive antibiotic prophylaxis for 3-5 days. Amoxicillin-clavulanate (Augmentin) given orally is an appropriate prophylaxis for most bite wounds. When cellulitis is present, longer courses of antibiotic, usually 7-14 days, are required. Hospitalization and surgical intervention may be required for more severe infections, osteomyelitis, joint infections, and in patients with complicating medical conditions.

Comprehension Questions

[43.11 Which of the following therapeutic options is common to the treatment of both bee stings and bite wounds?

A. Antibiotic prophylaxis with amoxicillin-clavulanate

B. Antihistamines for itching

C. Tetanus vaccination

D. Surgical wound debridement

|43.2] A 22-year-old woman develops a progressively enlarging red. hot area on her leg following a yellow jacket sting. She sees you in the office a day after the sting and says that the lesion is still enlarging. Which of the following statements is true?

A. This is an IgE-mediated reaction.

B. This is cellulitis that should be treated with antibiotic.

C. She should be prescribed an epinephrine kit to use if she gets stung again.

D. This type of reaction is unlikely to happen if she were to get stung again.

[43.3] You see a 7-year-old boy a day after he was bitten by his pet dog. According to the mother, the dog bit the child after he snuck up on the dog and grabbed its tail. The dog has had all its vaccinations, including rabies. The child has had no fever, has full movement of the injured limb, and has no sign of neurologic or vascular injury. The wound is on the child's forearm, is not deep, and is not bleeding, but has developed about 2 cm of erythema surrounding the site. Which of the following is the most appropriate treatment?

A. Hospitalization for IV antibiotic

B. Oral amoxicillin-clavulanate for 3-5 days

C. Oral amoxicillin-clavulanate for 7-14 days

D. Local care without any antibiotic


[43.1] C. Tetanus vaccination is common to the management of both bee stings and bite wounds. Bee stings rarely become infected and do not require antibiotic therapy.

[43.2] A. This patient is having a large, local reaction to her sting. This is an IgE-mediated reaction. It may respond to a course of oral steroid. There is at least a 50% chance that a similar reaction will occur if she were stung again, but she is unlikely to develop anaphylactic reactions in the future.

[43.3] C. This child is developing cellulitis from the bite wound. Based on his presentation, he does not appear to require hospitalization. He can be treated with oral antibiotics for 1-2 weeks.

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  • nunzia
    What immunization is appropiate for a insect bite or sting?
    13 days ago

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