What are Allergies?
Allergies are abnormal imune system reactions to things that are typically harmless to most people. When you’re allergic to something, your imune system mistakenly believes that this substance is harmful to your body. (Substances that cause allergic reactions, such as certain foods, dust, plant pollen or medicines are known as allergens)
In an attempt to protect the body, the imune system produces IgE antibodies to that allergen. Those antibodies then cause certain cells in the body to release chemicals into the bloodstream, one of which is histamine.
The histamine then affects the eyes, nose throat, lungs, skin or gastrointestinal tract and causes the symptoms of the allergic reaction. Future exposure to that same allergen will trigger this antibody response again. This means that everytime you come into contact with that allergen, you’ll have an allergic reraction.
Allergic reactions can be mild, like runny nose, or they can be severe, like difficulty breathing.
Laser light is a special kind of light.
Like ordinary light, it isade of waves, but there a three main differences. Ordinary light is a mixture of colors, laser light is judt one pure color. Besides, ordinary light wave have peaks and troughs, laser light waves line up perfectly. Also, an ardinary light beam spreads and fades, a laser light does not.
Lasesrs were invented in 1960. They are used tolay CDs and DVDs for music and movies, and in computers. They cut through thick metal in factories and carry out delicate eye operations. Theybcarry phone calls and television programs along cables. They even measure movement of the Earth to warn of volcanoes or eathquakes.
Laser beams can travel thousands of kilometers. To make a laser beam, energyy is fed in short bbursts into a substance called the active medium. The energy might be electricity, heat or ordinary light. In a ruby red laser, the active medium is a rod of ruby crystal.