Some of the most common allergens include:

• Pollen. Given off seasonally by trees, grass and weeds, pollen is responsible for triggering most cases of allergic rhinitis, also known as hay fever. The plant most commonly associated with pollen allergies is ragweed.
  
  

  

• Molds. Often found indoors where the humidity is high, mold can easily become airborne and trigger cases of allergic rhinitis year-round.
  
  

  

• Animal dander. Small scales or flakes of dead skin from animals (usually cats and dogs) are responsible for many allergic rhinitis symptoms.
  
  
• Dust Mites. These microscopic insects live in the dust found indoors and often trigger allergic rhinitis symptoms.
  
  
• Eggs. One of the most common types of food allergy, egg allergies are common in children, but are often outgrown.
  
  
• Milk. This type of food allergy involves a reaction to one or more of the proteins found in cow’s milk or dairy products. Like egg allergies, milk allergies are often outgrown.
  
  
• Wheat. The proteins found in wheat can trigger an immune system reaction in some people.
  
  
• Seafood. This type of food allergy is characterized by an allergic reaction to ingested fish or shellfish.
  
  
• Peanuts and tree nuts. These food allergies are triggered by peanuts, tree nuts (e.g., walnuts, almonds) or any product that uses peanuts or tree nuts as an ingredient. Highly sensitive individuals may react to even trace amounts picked up from utensils, surfaces or packaging machinery. Reactions can include anaphylactic shock.
  
  
• Soy. Most commonly found in infants, this type of allergy involves an immune response to soybeans, as well as foods and other products (e.g., some inks, soaps and dyes) that contain soy.
  
  
• Insect stings or bites. Some people experience serious or life-threatening reactions (anaphylaxis) after being bitten or stung by an insect.
  
  
• Penicillin. This common type of drug allergy can cause a range of symptoms including anaphylactic shock. The drug penicillin is commonly used to treat infections.
  
  
• Latex. Sensitivity to the sap in rubber trees causes some people to be allergic to latex products (made from rubber tree sap). Reactions to latex usually occur when skin-to-skin contact is made, but they are also possible through inhalation of small latex particles.
  
  
• Metals. Metals such as nickel, cobalt and chromate can trigger allergic reactions.
  
  
• Cosmetics. People can become allergic to any type of cosmetic or chemicals used in them. Cosmetics include makeup, skin-care creams, lotions, powders, sprays, perfumes, fingernail polishes, permanent waves, hair colors, deodorants, baby products, bath oils, bubble baths and mouthwashes. Fragrances cause more allergic reactions than any other cosmetic ingredient.
  
  
• Chemicals. Some people have allergic reactions to chemicals within household cleansing products. However, reactions can also occur in non-allergic people because many chemicals are irritants. Reactions can be related to contact (skin rash) or inhalation (wheezing) of these chemicals.
  
  
• Poisonous plants. Itchy bumps can form on the skin of some people sensitive to these plants.

  
  

• Sun, heat or cold. A variety of rashes may appear in sensitive people after exposure to sunlight or high temperatures. Conversely, some people can be allergic to cold temperatures.