Symptoms usually begin to develop immediately following an insect bite or sting. In most cases, they are mild and disappear within a day or two. Symptoms may include:

• Wound
• Mild pain
• Redness
• Swelling
• Itching
• Burning
• Numbness
• Tingling
• Rash
• Headache

Insects that sting leave their stinger in the flesh, which may be visible. Ticks attach to skin for several days and may still be visible at the site of the tick bite.

Symptoms of an allergic reaction to an insect sting may appear right away, or may be delayed as much as four hours to a week later. Symptoms of a mild allergic reaction to an insect sting include:

• Mild nausea
• Cramps
• Hives

• Itching (pruritus)
• Tenderness
• Diarrhea
• Red, warm, swollen lump more than 2 inches (5 centimeters) in diameter at the sting or bite site

A severe allergic reaction can be a life-threatening condition called anaphylaxis. Its symptoms may include:

• Intense itching, including areas other than the bite/sting site
• Feeling anxious
• Palpitations (an awareness of a strong, fast, irregular, abnormal or "galloping" heartbeat)
• Slurred speech
• Inability to swallow
• Swelling of the throat or tongue
• Rapid or weak pulse
• Red or swelling skin
• Hives (including on the lips, eyelids, throat and tongue)
• Cramps
• Diarrhea
• Nausea or vomiting
• Wheezing
• Bluish tint to skin (cyanosis), including lips or nail beds
• Coughing
• Choking
• Nasal congestion
• Difficulty breathing

Most cases of anaphylaxis involve either cardiovascular or respiratory symptoms, or both. More advanced symptoms of a severe allergic reaction may include:

• Collapse or loss of consciousness
• Convulsions
• Loss of bladder control
• Shock
• Stroke
• Cardiac arrest
• Respiratory arrest

Individuals experiencing severe allergic reaction or anaphylaxis require immediate medical attention.

Bites from some varieties of spider (which are arachnids, not insects) can lead to symptoms similar to a severe allergic reaction. Most spider bites are harmless. However, anyone who believes they may have been bitten by a poisonous spider should immediately contact a physician. Symptoms of such bites may vary depending on the type of spider, as follows:

• Black widow spider. Most who are bitten experience sharp pain and swelling at the bite site, which usually features two small fang marks. However, more serious symptoms can appear within 30 to 60 minutes and require immediate emergency medical attention. These include:
  
  
• • Deep blue or purple area around the bite, surrounded by a whitish ring and a large outer red ring
    
    
  • Muscle cramps and spasms at the bite site that increase and spread for 24 hours
    
    
  • Chills, fever, nausea and vomiting
    
    
  • Severe abdominal pain
    
    
  • Seizures
    
    
  • Stupor, restlessness and shock
    
    
  • Severe high blood pressure
    
    
• Brown recluse spider. Bites produce reddened skin and a blister at the bite site. Mild to intense pain and itching can follow for two to eight hours. An open sore with breakdown of the tissue (necrosis) also can develop within a few hours or days. This blackened tissue can take months to heal. Patients should seek medical care for necrosis, or any of the following symptoms:
  
  
• • Fever and chills
  • Skin rash over the body with tiny, flat purple and red spots
  • Nausea and vomiting
  • Joint pain
    
    
• Hobo spider. Symptoms include reddened skin that blisters within 36 hours. Numbness and tingling around the bite are common. About half of those bitten develop necrosis. Patients should see a physician if they develop necrosis or the following symptoms:
  
  
• • Headache
  • Weakness
  • Drowsiness
  • Vision problems
  • Hallucinations