Some microorganisms may multiply in the water overnight, but the harm to human body is not so serious. As long as it is not polluted, the nature of water will not change, so it is no problem to drink water overnight. The spring water we drink is probably more than 100 thousand years ago. For repeatedly boiled water, some people call it boiling water, which refers to the water repeatedly heated in a drinking machine or kettle. Generally speaking, the content of nitrite in this water will be higher. A large amount of nitrite can directly poison people, because nitrite reacts with human blood to produce methemoglobin, which makes blood lose its oxygen-carrying function and makes people suffer from hypoxia poisoning. Although the content of nitrite in boiled water is not so high, when nitrite reaches a certain dose in human body, it has carcinogenic, teratogenic and mutagenic effects, which can seriously endanger human health. Therefore, try not to boil water repeatedly. It is also best to "burn hot water as you drink it" in the water dispenser, and don't keep it in a state of "heating-insulation" all the time.
There used to be a saying that overnight tea can't be drunk, and it is easy to get cancer because it contains secondary amine, which can be converted into carcinogen nitrosamine.
In fact, this statement has no scientific basis, because secondary amines are widely found in many foods, especially in pickled products. Take bread as an example, it generally contains 2mg/kg of secondary amine. For example, if bread is the staple food, the daily intake of secondary amine from bread is 1- 1.5 mg.
When people drink tea, the only secondary amine they get from tea is bread? 0, can be ignored. Moreover, secondary amines themselves are not carcinogens, and nitrates must exist to form nitrosamines, which can only cause cancer if they reach a certain order of magnitude. Drinking tea can get more tea polyphenols and vitamin C from tea, which can effectively prevent the synthesis of nitrosamines in human body and is a natural inhibitor of nitrosamines. Therefore, drinking tea or overnight tea will not cause cancer.
However, from the point of view of nutrition and hygiene, tea soup is exposed to the air for a long time, which is easy to breed corrupt microorganisms and make tea soup deteriorate.
In addition, the tea soup is put for a long time, and the nutrients such as tea polyphenols and vitamin C are easy to be oxidized and reduced. Therefore, although overnight tea is harmless, it is generally better to drink it with the bubble.
Overnight tea is rich in alcohol and fluoride, which can prevent capillary bleeding. If you have oral bleeding, skin bleeding, ulcers and abscesses, you can use it to treat them. If the problem is the nose and mouth, you can wash your hands, rinse your mouth or drink it with overnight tea.
People with skin diseases can wash it, and those with red eyes or tears of unknown reasons can wash it with overnight tea, which has a good effect. Rinsing a few mouthfuls of overnight tea after brushing your teeth in the morning or before eating can not only make your mouth fresh and refreshing, but also strengthen your teeth. Some traditional Chinese medicines for treating rhinitis are also made of overnight tea.
In addition, washing your hair with overnight tea can relieve itching, promote hair growth and eliminate dandruff. People with sparse eyebrows brush their eyebrows with a brush dipped in overnight tea every day. After three to five months, their eyebrows will be thick and black. Bad breath contains overnight tea to gargle, which can reduce odor. Overnight tea can also remove oil stains and fishy smell.