What Is a Mild Allergic Reaction?

Drug allergic reactions, also known as drug allergies, are allergic reactions caused by drugs. They are a special type of adverse drug reactions. They are related to a person's specific allergic constitution and are only found in a small number of people. With the development of medical and health undertakings, the disease has an increasing trend, and its prevention must be paid great attention by doctors and patients themselves. Drug allergic reactions generally occur after multiple exposures to the same drug. The first episode has an incubation period, and the second episode can occur immediately. It occurs due to an abnormal immune response. This reaction is generally bad for the human body. Drug allergic reactions should generally have more typical allergic symptoms or signs. People with type I allergies often have rashes, itching, sneezing, runny nose, asthma attacks, and even systemic edema, decreased blood pressure, and shock. Those belonging to type II often have anemia, bleeding, and purpura. Those belonging to type III have fever, enlarged lymph nodes, joint swelling and pain, and kidney damage. Those belonging to often have eczema, fixed herpes, and clear skin pigmentation on the perimeter. The current evaluation of drug allergic reactions and the principle of treatment of drug allergic reactions are: first stop using allergenic or strongly suspected allergic drugs, followed by symptomatic treatment.

Basic Information

nickname

Drug allergy

English name

drug hypersensitivity

Visiting department

Allergy Section

Disease characteristics

Rash, itchy skin, asthma attack, bleeding, purpura, etc.

Clinical manifestations of drug allergic reactions

The drug enters the body through oral administration, injection, enema or other ways, causing a special systemic reaction. Some have various rashes on the skin, called drug dermatitis or drug rash; some only show internal organ damage; In addition to the rash, there are visceral damage. This article only discusses some typical drug rashes and a few specific types of drug allergic reactions.

Allergic drug rash

According to its incubation period, occurrence and development, rash manifestations and outcomes, it can be divided into at least 10 subtypes, such as fixed erythema drug rash, scarlet fever or measles-like drug rash, urticaria and angioedema drug rash, polymorphous erythema type Drug rash, nodular erythema-type drug rash, purpuric-type drug rash, eczema-like drug rash, acne-like drug rash, exfoliative dermatitis or erythrodermic type, and bullous epidermal necrosis-type drug rash. They have the following common features: have a certain incubation period, generally 4 to 20 days, with an average of 7 to 8 days, if they have been sensitized, the same drug is used again, usually within 24 hours, and the disease can occur within an average of 7 to 8 hours . The shortest is only a few minutes, and the late is not more than 72 hours. Most of them have sudden onset, or they may have precursor symptoms such as chills, discomfort, and fever. The rash occurs and develops. In addition to fixing the erythema, it is widespread and normal. Symmetrical distribution; often accompanied by systemic reactions of varying severity, which may not be obvious in severe cases, headache, chills, high fever, etc .; the course of the disease is self-limiting, the severity of which is about a week, and the severity does not exceed one Month; except for the prognosis of bullous epidermal necrolytic drug rash is poor, the rest are better. Several representative subtypes are introduced below.

(1) Urticaria and angioedema drug rash These drug rashes are relatively common. The rash is characterized by the occurrence of wind masses of varying sizes and lasting longer. Conscious itching can be accompanied by tingling and tenderness. May be accompanied by local swelling around the wind mass. The rash can appear as the only symptom, or as a symptom in sero-like syndrome and anaphylactic shock.

(2) Fixed erythema (fixed rash) drug rash is the most common type of drug rash, accounting for 22% to 44% of drug rash. The common pathogenic drugs are sulfa drugs (with long-acting sulfa drugs in the first place), tetracyclines, antipyretic analgesics and sedatives, edema patches, round or oval, clear edges, and one to several on severe patches Blisters or bullae. The number of erythema varies from one to several, and the distribution is asymmetric. Can occur in any part, often occur at the junction of the skin and mucous membranes such as lips and external genitalia, often caused by erosion caused by friction. If it recurs, it usually still occurs in situ, completely or partially overlaps with the pigmentation spots left over from the previous one, and often enlarges and increases compared with the previous one. Local skin lesions can be accompanied by itching, and those with extensive skin lesions have fever to varying degrees. After the erythema subsides, purple-brown pigmentation spots are often left, which do not recede for many years, and have diagnostic value. A few edematous erythema without purple fade quickly and leave no traces. Individual cases may be accompanied by polymorphous erythema-like drug rash, urticaria-like drug rash, or measles-like erythema.

(3) Scarlet fever-like or measles-like drug rash. The rash occurs suddenly, or it can be accompanied by chills, fever (above 38 ° C), headache, and general discomfort. The rash starts as a diffuse red spot or a half-grain-sized papule that develops from the face and neck, torso, and upper limbs to the lower limbs. It can spread throughout the body within 24 hours, with a symmetrical distribution, edematous, bright red, and faded when pressed. . In the future, the rash will increase and expand and merge with each other, which can affect the entire skin, just like scarlet fever. However, patients were generally in good condition without other manifestations of scarlet fever. After the rash developed to orgasm, the swelling gradually disappeared, followed by large scale desquamation, and after normal body temperature, the scales gradually became thinner and thinner, like pityriasis, and the skin returned to normal. The whole course of disease did not exceed one month, and there was generally no internal organ damage. If the rash is like measles, it is called pityriasis roseola. Sometimes the two rashes mentioned above can appear in the same patient at the same time.

(4) Severe polymorphic erythema drug rash This is a severe bullous polymorphic erythema. In addition to skin damage, serious mucosal damage to the eyes, mouth, and external genitalia occurs, with obvious erosion, exudation, and pain, often accompanied by chills, High fever can also be accompanied by bronchitis, pneumonia, pleural effusion, and kidney damage. Eye damage can cause blindness. More common in children with this type of drug rash.

(5) Exfoliative dermatitis or erythrodermic drug eruption It is characterized by redness and swelling of the skin throughout the body, accompanied by exudation and crusting, followed by exfoliation of large leafy scales. The exudate has an odor. Mucosa can also be congested, edema, erosion. Such rashes can occur systemically at the outset or develop on the basis of the scarlet fever-like or measles-like rash described above. Accompanied by obvious systemic symptoms, such as fever, nausea, vomiting, enlarged lymph nodes, proteinuria, liver enlargement, and jaundice. It is one of the more serious types of drug eruption, and its severity is second only to bullous epidermal necrolysis and lytic drug eruption. In the age of no corticosteroid use, its mortality rate is high. Due to the large dose or long course of treatment that causes this type of drug rash, it may be combined with certain toxic reactions based on allergic reactions.

This disease is characterized by a long incubation period, usually around 20 days; the course of the disease is long, usually at least one month.

The entire course of the disease can be divided into 4 stages: prodromal stage: manifested as a transient rash, such as symmetrical erythema confined to the chest, abdomen, or thigh, conscious itching, or accompanied by fever, this is a warning symptom, if at this time Withdrawal may prevent illness. rash period: it can slowly develop gradually from the face down, or start an acute attack, and later the rash will spread to the whole body quickly or slowly. At the climax of the rash, the whole body's skin was red and swollen, and facial edema was significant. Frequent scabs were associated with chills and fever. Some patients may have internal organ damage such as liver, kidney, and heart. The total number of white blood cells in peripheral blood is usually increased, generally between 15 × 10 ⁹ and 20 × 10 ⁹ / L. Exfoliation period: This is the characteristic manifestation of this disease. The rash redness began to subside, and then it was fish-scale to large-scale desquamation. The scales could be covered with sheets in the morning and repeatedly fall off, and lasted for 1 to several months. Hair and fingernails often fall off at the same time. Recovery period: fish scale-like desquamation or pityriasis, then gradually disappear, and the skin returns to normal. Since the application of corticosteroids, the course of disease can be significantly shortened, and the prognosis is greatly improved.

(6) Bullous epidermal necrotizing drug eruption is relatively rare in clinical practice and is the most severe type of drug eruption. The onset was urgent and the rash spread throughout the body within 2 to 3 days. Initially bright red or purple-red spots. Sometimes it appears as erythema polymorpha at the time of onset, and then increases and expands into a large brown-red patch. In severe cases, the mucosa is involved at the same time, which can be said to be incomplete. There are loose bullae on the spot, forming many parallel 3-10 cm long folds, which can be pushed from one place to another. The epidermis is very thin and breaks with a little rubbing, showing obvious spinous layer loosening. The whole body is often accompanied by a high fever of about 40 ° C. In severe cases, the organs of the gastrointestinal tract, liver, kidney, heart, and brain can be affected simultaneously or successively. The course of the disease is self-limiting, and the rash usually subsides after 2 to 4 weeks. If serious complications or severe involvement of some important organs occur, or due to improper treatment, they can die in about 2 weeks.

2. Several special types of drug allergic reactions

(1) Short-term antimony dermatitis type This is a mild toxic dermatitis seen in China during the short-term treatment of schistosomiasis in Japan with intravenous antimony potassium tartrate. Its characteristics are: high prevalence, generally 30% to 40%, and some can be as high as 60% to 70%. The incubation period is short, and they all occur within 2 to 3 days after starting treatment. After the amount of antimony agent reached 0.3 grams, rashes appeared. More common in summer. The rash is symmetrically distributed on the face, neck, back of the hands, and finger extensions. Occasionally, it appears in the chest and abdomen, resembles a mule, dense but not fused, mild inflammation, conscious slight itching or burning sensation, and individual systemic symptoms such as fever. The course of the disease is self-limiting. Even if the drug is not stopped, the rash mostly disappears within 3 to 5 days, accompanied by psoriasis-like desquamation. Retreatment occasionally has recurrence. No complications or sequelae were seen. Histochemical examination revealed no significant difference in antimony content between the rash and normal skin (both approximately 2.5 g / dl). Histopathology was similar to contact dermatitis and was nonspecific.

(2) Papillary hyperplasia type is mostly caused by long-term use of left iodine, bromine, etc., the incubation period is usually about one month, and gradually subsides after symptomatic treatment, the whole process is about 3 weeks.

(3) Lupus erythematosus-like reaction Since the discovery of hydralazine (hydrazine) in the early 1960s can cause lupus erythematosus-like reactions, more than 50 drugs such as penicillin, procainamine, isoniazid, Such reactions can be caused by aminosalicylic acid, butepine, methylthiouracil, reserpine, metronidazole, and oral contraceptives. Clinical manifestations include polyarthralgia, myalgia, polyserositis, pulmonary symptoms, fever, hepatosplenomegaly and lymphadenopathy, cyanosis of the extremities, and rash. However, laboratory tests were negative for anti-double-stranded DNA antibodies and normal complement values; clinical symptoms were mild; renal and central nervous system infestations rarely occurred; symptoms subsided after drug discontinuation, and these were different from idiopathic lupus erythematosus.

(4) Fungal disease type reactions Due to the application of a large number of antibiotics, corticosteroids and immunosuppressants, it often causes disturbance of the internal environment balance and flora imbalance, and there is a case response of fungi, manifested as Candida albicans, Aspergillus or Dermatophyte infection. The first two can have gastrointestinal, lung, or other visceral infections and can involve multiple organs at the same time. It is not uncommon to find severe systemic fungal infections during autopsy of immunosuppressant patients during their lifetime. It is worth noting that some patients with dermatophytosis, due to the application of the above-mentioned drugs, the skin lesions of ringworm have become more extensive and difficult to treat. Even if cured, it is easy to relapse, causing difficulties in the prevention and treatment of ringworm.

(5) Corticosteroid type reactions If the dosage of hormone is large and the time is long, it can often cause a variety of adverse reactions and even cause death. The main side effects it causes are: secondary bacterial or fungal infections: most common. gastrointestinal tract: steroid ulcers, even with blood and perforation. Central nervous system: euphoria, irritability, dizziness, headache, insomnia, etc. Cardiovascular system: palpitations, elevated blood pressure, thrombosis, arrhythmia, etc. Endocrine system: Cushing-like syndrome, osteoporosis, diabetes, hypocortex, and growth and development inhibition in children. skin: acne, hairy, dilated capillaries, ecchymosis, skin atrophy, etc. Squint: blurred vision, increased intraocular pressure, cataracts and glaucoma.

Drug allergy test

In laboratory tests, skin scratches and intradermal tests are commonly used to detect patients' sensitivity to penicillin or iodide, which is of some value in preventing anaphylactic shock, but it has little significance in preventing the occurrence of drug rash. In vitro tests, lymphocyte transformation tests, and radioallergen adsorption tests have been used for the detection of clinical allergens, but they are only reliable for some drugs and can be used under conditions and have certain reference value.

Diagnosis of drug allergic reactions

Given the wide range of drug responses, their complex performance, and their specificity, it is sometimes difficult to make a diagnosis. For the diagnosis of drug rash, the clinical history is still the main basis, combined with rash manifestations, skin scratches, intradermal tests, etc., and the possibility of other diseases is excluded, and comprehensive analysis and judgment are performed.

Drug allergy treatment

Remove the cause

Discontinuing all suspicious disease-causing drugs is the first measure to take, and don't continue to use the drug when there are already aura symptoms of drug allergic reactions.

2. Supportive Therapy

Give the patient favorable conditions and avoid unfavorable factors, in order to smoothly pass through the self-limiting course of disease, such as bed rest, diet rich in nutrients, maintaining a suitable cold and warm environment, and preventing secondary infections.

3. Strengthen excretion

Use laxatives and diuretics as appropriate to promote the excretion of drugs from the body.

4. Drug treatment

(1) Mild cases: 1 or 2 antihistamines are taken orally. Intravenous injection of vitamin C. Intravenous injection of 10% calcium gluconate or 10% sodium thiosulfate. Calconite lotion containing camphor or mint can be applied to the external extremities several times a day to relieve itching, heat dissipation, and anti-inflammatory. Generally, it can be cured in about a week.

(2) Severe cases: Rest in bed. Apply the above medicine. Prednisone is taken orally, and it usually recovers in about 2 weeks.

(3) Serious cases:

1) Corticosteroids: Hydrocortisone, vitamin C, 10% potassium chloride and 5% to 10% glucose solution are slowly instilled, and continuous infusion should be maintained for 24 hours. When the body temperature returns to normal, when the rash mostly subsides and the blood is normal, the hormone dosage can be gradually reduced until a considerable amount of prednisone or dexamethasone is taken orally. If the rash subsides, the general condition improves, and then gradually reduce the oral dose of hormones. The principle is that each reduction is 1/6 to 1/10 of the daily dose. Each reduction requires observation for 3 to 5 days. Pay attention to the reduction at any time. Rebound phenomenon. The problem in treating severe drug eruption is often the improper dosage or usage of hormones, such as the initial dose is too small or it is reduced too quickly in the future.

2) Antihistamines: Choose two oral drugs at the same time.

3) Transfusion of fresh blood and plasma.

4) Antibiotics: Appropriate antibiotics are used to prevent infection, but care must be taken. Patients with severe drug rashes are often in a highly allergic state. Not only are they prone to cross-allergy of drugs, but they may also be polygenic, which means they are sensitive to the original Structurally completely unrelated drugs create allergies and cause new drug rashes.

5) Local treatment: Local treatment and care for skin and mucosal damage in patients with severe drug eruption is very important and often becomes the key to success or failure of treatment. In the early acute stage, a large amount of powder or calamine lotion can be used for skin lesions to protect the skin and reduce inflammation and swelling. If there is any exudate, use saline or 3% boric acid solution for wet compress and change it 4-6 times a day. After drying, use 0.5% neomycin and 3% sugar distillate paste, 1 or 2 times a day.

The conjunctiva and cornea are often affected and must be treated in a timely manner. It can be rinsed with normal saline or 3% boric acid water to remove secretions, and drip triamcinolone or hydrocortisone eye drops every 3 to 4 hours. Rub boric acid or hydrocortisone eye cream every night to prevent blindness and conjunctival adhesions due to corneal exfoliation. Oral and lip mucosal damage often prevents eating, and can be rinsed with compound borax liquid, mucosa ulcer cream or pearl yellow powder, tin powder and so on. Nasal feeding can be used for those who cannot eat.

6) If it is accompanied by damage to the organs of the heart, lungs, liver, kidneys, and brain, and hematopoiesis, etc., it should be dealt with in a timely manner.

7) Pay close attention to the balance of water and electrolytes, and give drugs such as adenosine triphosphate, coenzyme A, inosine, and vitamin B ₆ as appropriate.