Signs and symptoms of an insect bite result from the injection of venom or other substances into your skin. The venom triggers an allergic reaction. The severity of your reaction depends on your sensitivity to the insect venom or substance.
Most reactions to insect bites are mild, causing little more than an annoying itching or stinging sensation and mild swelling that disappear within a day or so. A delayed reaction may cause fever, hives, painful joints and swollen glands. You might experience both the immediate and the delayed reactions from the same insect bite or sting. Only a small percentage of people develop severe reactions (anaphylaxis) to insect venom. Signs and symptoms of a severe reaction include facial swelling, difficulty breathing and shock.
Bites from bees, wasps, hornets, yellow jackets and fire ants are typically the most troublesome. Bites from mosquitoes, ticks, biting flies and some spiders also can cause reactions, but these are generally milder.
For mild reactions:
- Move to a safe area to avoid more stings.
- Scrape or brush off the stinger with a straight-edged object, such as a credit card or the back of a knife. Wash the affected area with soap and water. Don't try to pull out the stinger; doing so may release more venom.
- To reduce pain and swelling, apply a cold pack or cloth filled with ice.
- Apply 0.5 percent or 1 percent hydrocortisone cream, calamine lotion or a baking soda paste — with a ratio of 3 teaspoons baking soda to 1 teaspoon water — to the bite or sting several times a day until your symptoms subside.
- Take an antihistamine containing diphenhydramine (Benadryl, Tylenol Severe Allergy) or chlorpheniramine maleate (Chlor-Trimeton, Teldrin).
Allergic reactions may include mild nausea and intestinal cramps, diarrhea or swelling larger than 2 inches in diameter at the site. See your doctor promptly if you experience any of these signs and symptoms.
For severe reactions:
Severe reactions may progress rapidly. Dial 911 or call for emergency medical assistance if the following signs or symptoms occur:
- Difficulty breathing
- Swelling of your lips or throat
- Faintness
- Dizziness
- Confusion
- Rapid heartbeat
- Hives
- Nausea, cramps and vomiting
Take these actions immediately while waiting with an affected person for medical help:
- Check for special medications that the person might be carrying to treat an allergic attack, such as an auto-injector of epinephrine (for example, EpiPen). Administer the drug as directed — usually by pressing the auto-injector against the person's thigh and holding it in place for several seconds. Massage the injection site for 10 seconds to enhance absorption.
- After administering epinephrine, have the person take an antihistamine pill if he or she is able to do so without choking.
- Have the person lie still on his or her back with feet higher than the head.
- Loosen tight clothing and cover the person with a blanket. Don't give anything to drink.
- If there's vomiting or bleeding from the mouth, turn the person on his or her side to prevent choking.
- If there are no signs of circulation (breathing, coughing or movement), begin CPR.
If your doctor has prescribed an auto-injector of epinephrine, read the instructions before a problem develops and also have your household members read them.
source: http://www।mayoclinic।com/
Some ticks transmit bacteria that cause illnesses such as Lyme disease or Rocky Mountain spotted fever. Your risk of contracting one of these diseases depends on what part of the United States you live in, how much time you spend in wooded areas and how well you protect yourself. 
