Did you have any interesting dreams last night? Do you know everyone dreams? But not everyone remembers their dreams. A person can usually have up to seven dreams a night, and each dream usually lasts from 10 to 40 minutes.

Why do we dream? Scientists believe that we dream to remember because dreams come from our memories and they tell us a lot about ourselves. They also help us hear from the past and even help us solve problems.

Different dreams mean differently to people. For example, if you dream about flying, you are probably quite happy. This is a good time in your life. You may feel that other people see you as a leader. And when you dream that you didn’t study for a test, it usually means you are worried about an important thing coming in your life.

Every time you cat seafood, you get red spots（红点）on your body. And every spring and fall, your friend gets a runny nose when you play in the garden. What’s going on? Well, you and your friend may have allergies（过敏）.

An allergy is a reaction from your immune system（免疫系统）. The immune system keeps you away from diseases by fighting germs（细菌）. But when you have allergies, it overreacts（过度反应）and tries to fight against things like grass, pollen or some foods. This makes your body feel uncomfortable.

Allergies are common around the world. According to the WHO, about 20 percent of the world’s population suffers from allergies.

Food allergies are one of the most common types. Many children can be allergic to food like milk, eggs and peanuts. If you are allergic to certain foods, you may get red spots, an upset stomach or even have difficulty breathing. So far, people haven’t found any good ways to stop food allergies. Just do not eat those foods as much as possible.

Seasonal allergies happen in most parts of the world. So how do you know if you are allergic to something? Skin（皮肤）tests are the most widely used way.

Different weather makes people feel different. Weather influences health, intelligence（智力）and feelings.

In August, it is very hot and wet in the southern part of the United States. People there have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot in summer and very cold in winter. People in these states have more heart trouble when the weather changes in February or March.

The weather can also influence intelligence. For example, in a 1983 report by scientists, the IQ of a group of students was very high when a very strong wind came, but after the strong wind, their IQ was 10% lower. The wind can help people have higher intelligence. Very hot weather, on the other hand, can make it lower. Students in many schools in the United States often get worse on exams in the hot months of the year (July and August).

Weather also has a strong influence on people’s feelings. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel unhappy during cold weather, too. But fat people may have a hard time in hot summer. At about 18℃, people become stronger.

Low air pressure（气压） may make people forgetful. People leave more bags on buses and in shops on low-pressure days.

Are you feeling sad, tired, or forgetful today? It may be the weather’s problem.