Original title: Why do some people get red spots and others get big bags after being bitten by mosquitoes?

After the beginning of summer, the weather in Beijing is getting hotter. As the temperature rises, mosquitoes are ready to move again! Mosquitoes are such small things that people hate to itch, but they have no choice. The annoying buzz echoes in our ears, not only interfering with our lives, but also leaving a unique "mark" on our bodies. These "marks" sometimes appear as conspicuous bags, sometimes as small red dots. So, what's the secret behind this?

How do mosquitoes suck blood?

Mosquitoes will first use their innate sense of smell to find suitable targets through human exhaled carbon dioxide and excreted body fluids. When the target is found, the mosquito will stab the sharp mouthpiece into the human skin.

Mosquito mouthparts are actually complex structures composed of many parts. There are six "needles" on the mosquito's head, two of which are serrated and are the main tools for committing crimes.

These include the "knife" that can cut the skin and the detection structure used to find blood vessels. When blood vessels are found, the mosquito will inject saliva containing anticoagulant substances into the wound through the pipe in the mouthpiece to prevent blood coagulation and facilitate its ingestion. Then, mosquitoes use muscle contraction and relaxation to suck blood into their bodies.

Different conditions after being bitten by mosquitoes are related to the toxicity of mosquitoes and immune system

After blood sucking, the mosquito will fly away, and the bitten part may show itching, redness and swelling, which is mainly due to the immune response caused by some special substances released by the mosquito.

After being bitten by mosquitoes, there are different situations. Some people have larger bags, while others have smaller red spots. The reason is mainly related to the toxicity of mosquitoes and the reaction degree of our own immune system.

The constituent elements of the immune system include immune cells, immune organs and immune substances. Its main responsibility is to fight against foreign pathogens and mutated cells in the body to ensure the health of the human body. In normal human body fluids such as blood, tissue fluid, secretory fluid and other body fluids, there are many substances with the efficacy of killing or inhibiting pathogens, such as lysozyme, defensins, phagocytic bactericides, histones and so on. When pathogenic microorganisms such as bacteria and pathogens invade the human body, macrophages in the immune system will first decompose them into fragments, then present them on their own surface and become antigens.

When the pathogen enters the body's blood, lymph and other parts, B cells (lymphocytes from bone marrow, participating in humoral immunity) will be stimulated by external antigens to change their shape, increase their size, and transform into plasma cells, which can secrete antibodies to specifically bind and remove the antigens, thus exerting the humoral immune function; When pathogens enter the cell, T cells (lymphocytes from the thymus, which participate in cellular immunity) can play a cytotoxic role, clean up the antigen or foreign matter, and maintain human health. After the infection is suppressed for the first time, the immune system will leave a memory of the pathogenic substance, so that if the same pathogenic substance invades again in the future, it can respond accurately and quickly.

If you are frequently bitten by the same mosquito, the immune system will gradually become "numb"

Generally speaking, after being bitten by mosquitoes with strong toxicity (such as mosquitoes), the body will have strong symptoms and itching. If you have never been bitten by a mosquito before, the situation will be more special when you first encounter it. When the mosquito inserts the mouthpiece into the blood vessel of your subcutaneous tissue, it will secrete some substances from the salivary gland. These substances are used to prevent blood coagulation and ensure that the mouthpiece can be pulled out smoothly. When the mosquito finishes sucking blood and pulls out the mouthpiece, the capillary will bleed and form a small silt. In addition, mosquito secretions work together to trigger a slight inflammatory reaction, so what we see is a small red dot.

At this time, because our immune system has not yet recognized this "foreign matter", it will not immediately form mosquito packets. However, the immune system is not indifferent, it will silently remember this "uninvited guest". The next time the same mosquito bites, the immune system will respond quickly and call up many immune cells in a few seconds. These immune cells will produce histamine, cytokines and other substances, which are like "signal soldiers", transmitting the instructions of the body. Histamine can cause telangiectasia and itching; Cytokines will further induce inflammation, so the original small red dot will become a big and itchy mosquito bag.

Interestingly, if you are frequently bitten by the same mosquito, the immune system will gradually become "numb". Just like soldiers who have been in the battlefield for a long time, they become accustomed to familiar enemies and no longer have strong reactions. This explains why over time, the body's response to mosquito bites will gradually decrease, and the mosquito bag will not be so obvious.

Disturbance, protection and post treatment of mosquito bites

When we are accidentally bitten by mosquitoes, we also need to take corresponding treatment methods for large bags and small red spots. For large bags, cold compress can be used to reduce swelling and itching. Cold compress can shrink blood vessels and alleviate inflammatory reaction. For small red spots, apply some antipruritic ointment to help relieve itching. But it should be noted that you should never scratch too much, because scratching not only aggravates itching, but also may lead to skin damage and infection. Once infection occurs, it may lead to more serious consequences.

In a word, it is very important to understand the relevant knowledge and precautions of mosquito bites. Through in-depth understanding of the principles and coping methods of mosquito bites, we can better protect ourselves and reduce the trouble of being bitten by mosquitoes.

(The article comes from the WeChat official account Digital Beijing Science Center)