Background: An allergy is a disease in which the immune system makes an inflammatory response to a harmless antigen . Any antigen that causes an allergy is called an allergen. Allergens may be inhaled or ingested, or they may come into contact with the skin. Two common causes of allergies are shown in Figure below . Inhaling ragweed pollen may cause coughing and sneezing. Skin contact with oils in poison ivy may cause an itchy rash. Other common causes of allergies include dust mites, mold, animal dander, insect stings, latex, and certain food and medications. Symptoms of a common allergy such as pollen can include sneezing, a runny nose, nasal congestion and itchy, watery eyes.

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who is allergic to ragweed?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who is allergic to poison ivy?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who is having an allergic reaction?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who came into contact with something harmless?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who's immune system is reacting to something harmless?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who's having an inflamitory response?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who touched an allergen?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who inhaled an allergen?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who is likely to also have watery eyes?

Situation: Mark and Jane were working in their yard planting a garden and mowing. Jane was sneezing and coughing much of the day. Mark was fine until he pulled up some weeds and noticed that his arms were inch and had red bumps all over them.

Question: Who came in contact with a plant oil?