The skin itches and turns red when scratched

We have all experienced this. If we encounter something in life that is allergic to our body, or something that can make our skin uncomfortable, our skin will become itchy in large areas, and if we scratch it, large areas of red will appear. So let’s take a look at this situation below!

1. Skin scratching

Dermatographism, also known as artificial urticaria, refers to the condition in which the skin is scratched with fingernails or a blunt object, causing the skin to swell up and appear as cord-like lumps (medically, these cord-like lumps are called wheal scratches). This disease can be divided into two types: simple symptomatic and simple scratching. Simple scratching is a physical abnormality of normal people, and about 5% of normal people have this phenomenon. Symptomatic scratching is divided into immediate and delayed types, both of which are caused by allergic reactions. The common pathogen of the former is penicillin. This kind of allergy does not necessarily have a drug reaction first. 80% of patients treated with penicillin have positive skin scratch tests, and some patients still have positive results long after stopping penicillin. In addition to penicillin, if the patient has a recent bacterial infection (such as acute tonsillitis, cholecystitis, appendicitis, etc.) or insect bites, it may also cause immediate symptomatic skin scratches. The onset of delayed symptomatic skin scratching is related to fungal allergy, and the antigen is often a fungal product, so patients with tinea pedis are prone to delayed symptomatic skin scratching.

Simple dermatographism usually does not require treatment. For symptomatic skin scratches, the causative factors should be found and eliminated as much as possible. For example, patients who are taking penicillin should stop taking penicillin immediately; those with bacterial infections should receive anti-infection treatment; those with fungal infections such as tinea pedis can receive anti-fungal treatment, etc. Secondly, antihistamines such as chlorpheniramine and antalol can be used, which have certain therapeutic effects. In addition, some drugs that reduce the permeability of blood vessel walls, such as vitamin C, calcium supplements, etc., can be used as an auxiliary. It is worth noting that penicillin should not be used to treat patients with skin scratches who also have other infectious diseases.

Scratch disease is also called artificial urticaria, skin scratch rash, or mechanical urticaria, which is a special type of urticaria.

2. There are two types of skin scratches: one is called simple skin scratches, which is more common in women and is a physiological abnormal physical reaction. The symptoms are wheals that appear after the skin is scratched by nails or other blunt objects, which are usually not accompanied by itching or other discomfort.

Another type of skin scratching is called symptomatic skin scratching, which is common in young people with allergic constitution. The cause of its occurrence is mostly due to the allergic reaction of the skin after external physical stimulation, which causes mast cells to release biologically active substances such as histamine, causing the skin capillaries to dilate, the permeability to increase, and the plasma and tissue fluid to penetrate into the dermis. People suffering from this skin scratching disease often feel itchy skin for no reason, but unlike the common urticaria, they do not have wheals all over the body. Instead, when the skin is scratched with nails or other blunt objects, erythematous wheals appear locally first, and then the wheals swell up above the skin, and red halos appear at the edges of the erythematous wheals. Their shape is very similar to the marks left after the skin has been whipped with a whip. Some patients with severe symptoms may even experience swollen lips after their lips are bitten by teeth.