Allergies once system reacts to substance — like spore, bee venom or pet dander — or a food that does not cause a reaction in most people. Your immune system produces substances known as antibodies.
When you have allergies, your system makes antibodies that identify a particular matter as harmful, although it's not.
When you get contact with the matter, your immune system's reaction will inflame your skin, sinuses, airways or digestive system.