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A drug rash, sometimes called a drug eruption, is a reaction your skin can have to certain drugs.

Causes

Almost any drug can cause a rash. But antibiotics (especially penicillins and sulfa drugs), NSAIDs, chemotherapy agents and anti-seizure drugs are common drugs to cause a rash. The most common antibiotics causing drug eruptions include amoxicillin, trimethoprim sulfamethoxazole, ampicillin, penicillin, cephalosporins, quinidine and gentamicin sulfate. Drug eruptions can imitate a variety of other skin conditions and should be considered in any patient taking medications or that has changed medications. 

Symptoms

The onset of drug eruptions is usually within 2 weeks of beginning a new drug or within days if it is due to re-exposure to a certain drug. Itching is the most common symptom. Drug eruptions occur in approximately 2-5% of hospitalized patients and in greater than 1% of the outpatient population. Adverse reactions to drugs are more prevalent in women, in the elderly, and in immunocompromised patients.

Types of Hypersensitivity

Drug eruptions may be immunologically or non-immunologically mediated. There are 4 types of immunologically mediated reactions, where Type IV hypersensitivity being the most common. 

Type I – immunoglobulin-E dependent (result in anaphylaxis, angioedema, urticaria)

Type II – cytotoxic (result in purpura)

Type III – immune complex reactions (result in vasculitis)

Type IV – delayed-type reaction (contact dermatitis and photoallergic reactions)

Here are some examples for drug causing eruptions:

Insulin – type I reactions 

Penicillin, cephalosporins, and sulfonamides – type II reactions

Quinines and salicylates – type III reactions 

Topical medications such as neomycin – type IV reactions

The important role of Medical history
A complete medical history and a thorough review of the patient’s medication list including over-the-counter drugs such as vitamins, herbs, minerals, and other homeopathic regimens are important in working up a diagnosis. It is also essential to note the time between the introduction of a drug and onset of the eruption along with the route and dose of the drug taken. Previous adverse reactions to any medications should also be noted.

Drug eruptions have a wide range of morphological features although the majority of patients present with a generalized exanthematous or morbilliform eruption. Other physical manifestations include acneiform papules and pustules where comedones are absent, alopecia, tenderness and redness on the palms and soles, target lesions seen in erythema multiform tender, erythematous nodules seen in erythema nodosum  and round, violaceous plaques that fade with macular hyperpigmentation as seen in fixed drug eruptions. Wheals may be seen in an urticarial-type of drug eruption and tender erythematous papules and plaques may be seen in drug-induced Sweet’s syndrome. 

It is important to check for certain features that may indicate a potentially life-threatening drug reaction (toxic epidermal necrolysis, Steven Johnson syndrome, hypersensitivity syndrome, and serum sickness) such as mucous membrane erosions, blisters, a positive Nikolsky’s sign, high fever, shortness of breath and skin necrosis.

Common rash due to drug reaction

(1) Exanthematous Rash

This is the most common type of drug rash, making up about 90 percent of cases. It’s marked by small lesions on reddened skin. These lesions can be either raised or flat. Sometimes, you might also notice blisters and pus-filled lesions.

Common causes of exanthematous drug rashes include:

• penicillins
• sulfa drugs
• cephalosporins
• anti-seizure drugs
• allopurinol

(2) Urticarial Rash

Urticaria (hives) is the second most common type of drug rash. They’re small, pale red bumps that can form larger patches. Hives are usually also very itchy.

Common causes of urticarial drug rashes include:

• non-steroidal anti-inflammatory drugs (NSAIDs)
• ACE inhibitors
• antibiotics, especially penicillin
• general anesthetics

(3) Photosensitivity Rash

Some drugs can make your skin extra sensitive to UV light. This can result in an itchy sunburn if you go outside without proper protection.

Drugs that tend to causes of photosensitivity include:

• certain antibiotics, including tetracycline
• sulfa drugs
• antifungals
• antihistamines
• retinoids, such as isotretinoin
• statins
• diuretics
• some NSAIDs

(4) Erythroderma

This type causes nearly all of the skin to become itchy and red. The skin may also grow scaly and feel hot to the touch. Fever might also occur.

Many drugs can cause erythroderma, including:

• sulfa drugs
• penicillins
• anti-seizure drugs
• chloroquine
• allopurinol
• isoniazid

Warning : Erythroderma can become serious and life-threatening. Seek immediate medical attention if you think this is the type of rash you have.

(5) Stevens-Johnson Syndrome (SJS) and toxic epidedmal necrosis (TEN)

SJS and TEN are considered the same condition, but there’s a slight difference between them:

• SJS involves less than 10 percent of the body.
• TEN involves more than 30 percent of the body.

SJS and TEN are marked by large, painful blisters. They can also cause large areas of the top layer of your skin to come off, leaving raw, open sores.

Common drug-related causes include:

• sulfa drugs
• anti-seizure drugs
• some NSAIDs
• allopurinol
• nevirapine

Warning : SJS and TEN are serious reactions that can be life-threatening. They both require immediate medical attention.

(6) Anticoagulant-induced skin necrosis

Some blood thinners, such as warfarin, can cause anticoagulant-induced skin necrosis. This causes the skin to become red and painful.

Eventually, the tissues beneath the skin die. It usually only happens at the start of taking a very high dose of a blood thinner.

Warning : Anticoagulant-induced skin necrosis is a serious reaction that requires immediate medical attention.

(7) Drug reaction with eosinophilia and systemic symptoms(DRESS)

DRESS is a rare type of drug rash that can be life-threatening. It can take two to six weeks for symptoms to appear after starting a new drug.

A DRESS rash looks red and often begins on the face and upper body. Accompanying symptoms are severe and can involve the internal organs. They include:

• fever
• swollen lymph nodes
• facial swelling
• burning pain and itchy skin
• flu-like symptoms
• organ damage

Drugs that can cause DRESS include:

• anticonvulsants
• allopurinol
• abacavir
• minocycline
• sulfasalazine
• proton pump inhibitors

Warning : DRESS is a very serious reaction that requires immediate medical attention.

Treatment

Treatment includes identifying and withdrawing the offending agent as soon as possible. A biopsy may be helpful in establishing a diagnosis of a drug reaction. 

For mild drug eruptions

Treatment is supportive with anti-histamines, topical or oral steroids, and moisturizing lotions. Most patients with mild drug eruptions should expect clearing in approximately 1-2 weeks with no complications. All patients should be educated to avoid the offending agent to prevent further complications.

For Severe drug reactions

Admission to the hospital for a more thorough work-up. Intravenous immunoglobulin may be given to treat toxic epidermal necrolysis and systemic steroids may be given in the treatment of hypersensitivity reactions. 

Skin allergy test

With a skin test, the allergist or nurse administers a small amount of a suspect drug to your skin either with a tiny needle that scratches the skin, an injection or a patch. A positive reaction to a test will cause a red, itchy, raised bump. A positive result suggests you may have a drug allergy.

Dr. Aye Min Htoo

Dermatologist

If you have been suffering from some of the above symptoms, you should contact a local dermatologist or by calling 092051590 for further advanced treatment.

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