General information
Undesirable reactions and side effects of antibiotics often show up on the skin. In most cases, harmless skin rashes occur, which subside by themselves when the medication is no longer taken. Very rarely, more serious complications can also occur due to the antibiotic effect.
Particularly in older people, skin changes often occur after taking antibiotics because the liver and kidney function is weakened and therefore the antibiotics can be broken down and excreted more slowly. In addition, the risk of side effects such as a skin rash from antibiotics increases when several drugs are taken at the same time, as is often the case with older people. This can lead to interactions between the different substances and the risk of skin reactions increases.
Symptoms
Undesirable side effects of antibiotics can basically occur in all organs, for example the liver can be severely damaged. But most often the skin reacts to substances in drugs. A skin rash caused by an antibiotic can look very different.
The variations range from small, rubella-like spots to large, slightly raised pustules like measles. Bubbles filled with liquid can also form, so-called wheals, and the rash can spread over the entire body. More rarely, other forms may also occur – the rash may look net-shaped, show small bleedings or extensive redness.
The rash does not have to cause any symptoms at all, sometimes itching occurs. In most cases, the rash does not appear until about two to five days after starting to take the antibiotic, but allergic reactions can also occur immediately after taking the antibiotic. The greatest danger then is a so-called anaphylactic shock, an allergic reaction that can lead to shortness of breath.
Itching is a common side effect of drug exanthema. The exact mechanism of itching is not fully understood. However, it is assumed that it is not mediated by pain receptors but by free nerve endings.
Substances such as histamine, which is released by white blood cells during pseudoallergic reactions such as drug exanthema, stimulate these nerve endings. Obviously, however, the sensation can be overlaid by other stimuli such as cold or heat. For this reason, cooling the itchy skin often helps.
Warm water can also prevent itching. Apart from this, an antihistamine can be prescribed for severe itching. The antibiotics that probably lead most often to unwanted skin rashes are the so-called betalactam antibiotics.
About 3% – 10% of all people who receive such an antibiotic react with a skin rash. Only about one third of those affected have a real allergic reaction to the drug. In most people, the reaction on the skin is mediated by pseudoallergic reactions, the exact mechanism behind this is not yet fully understood.
Pfeiffer’s glandular fever is another common cause of a skin rash after taking antibiotics. Pfeiffer’s glandular fever is an infection with the Epstein-Barr-Virus (EBV), against which no antibiotic is effective because antibiotics are only effective against bacteria. However, the diagnosis of the disease is not easy, often a bacterial infection is suspected.
If an affected person with whistling glandular fever wrongly receives the antibiotic amoxicillin, a skin rash almost always develops, which is caused by the interaction of the viruses and the antibiotic. In rare cases, a severe immune reaction can also occur, and a so-called Stevens-Johnson syndrome or Lyell syndrome, in which the skin becomes detached and painful blisters and mucous membrane ulcerations develop. Especially the group of sulfonamide antibiotics is known for this.
Amoxicillin is a very common antibiotic, which is related to the penicillins, but has a wider spectrum of activity than the penicillins. This makes it a suitable medication for respiratory tract infections and middle ear infections. At this point it is important to know that antibiotics are only effective against bacteria and in few cases against parasites and fungi, but not against viruses.It is not uncommon, however, to prescribe an antibiotic for viral infections when the bacterial cause of the symptoms is suspected.
This is often not only useless, but can also have serious side effects. For example, amoxicillin can cause pseudoallergies if it is prescribed when streptococcal angina is suspected, but a viral infection is actually present. Classically, drug exanthema caused by amoxicillin occurs mainly when the patient is suffering from so-called infectious mononucleosis, also known as whistling glandular fever.
This disease is the result of an infection with the Epstein-Barr virus, the symptoms of which can resemble those of angina. Why the combination of the virus and amoxicillin causes the sometimes severe skin rashes is still not known today. However, as soon as the antibiotic is identified as the cause of the exanthema, discontinuation of the drug is the most important measure.
As with other drug exanthemas, the application of an ointment containing cortisone can provide relief. Apart from this, a procedure including possible testing for the Epstein-Barr virus should be discussed with the treating physician. A large number of different drugs are now known to trigger phototoxic reactions when combined with UV light.
This means that under the influence of UV light, substances can be formed that have a damaging or toxic effect on the tissue. This process can be triggered by sunlight, but even more so by light used in a solarium. The reactions thus represent a special form of the drug exanthema and can occur both with external application, as well as taking the drugs.
Beside certain pain means, Neuroleptika, Vitamin A preparations for acne therapy and even vegetable preparations from Johanniskraut, Baldrian and Arnika are above all antibiotics for it admits strongly phototoxic to work. In highest place here the antibiotic Doxycyclin stands. Afterwards follow further substances of the group of the Tetracyclin antibiotics, in addition, so mentioned Gyrasehemmer. In order to clarify whether photosensitization is actually present for a drug, a test with UV-A and UV-B light in ascending intensity can be performed. For this purpose, however, the suspected drug must not be discontinued before.
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