What Is Drug-induced Photosensitivity?

It's estimated that around 3,000 medications can cause photosensitivity reactions. What does this problem consist of? What are the symptoms? Read this article to discover everything you need to know.

Drug-induced photosensitivity is quite common. In fact, researchers estimate that around 3,000 medications can cause this effect. It can appear as a phototoxic reaction or as a photoallergic reaction.

Due to this, all phototoxic or photoallergic reactions are photosensitivity reactions, but not all photosensitivity reactions are either phototoxic or photoallergic. All of these are abnormal reactions that occur on the skin after sun exposure and after taking certain medications.

During the summer, it’s especially important to be careful with this type of problem. For this reason, both health specialists and patients should be informed about what these drugs are and what reactions they can cause.

What is drug-induced photosensitivity?

As we mentioned, this condition is a skin reaction that occurs when the sun’s rays strike the skin and interact with certain chemical compounds in photosensitive medicine.

These compounds, which react with the light spectrum between visible light and ultraviolet radiation, can be both the active ingredient and one of the excipients that are part of the formula.

It’s worth mentioning that photosensitivity reactions make up 8% of all adverse drug reactions, and skin pigmentation is among the risk factors. In fact, the more pigmented it is, the greater the probability of suffering these reactions.

In addition to pigmentation, other population groups are susceptible. Among them we find the following:

• Patients who are under treatment with NSAIDs for chronic pain.
• Cancer patients who are being treated with chemotherapy.
• People with a psychiatric illness treated with phenothiazines.
• Patients with high blood pressure who take thiazide diuretics as treatment.
• Finally, the elderly and patients with a weak immune system.

What is a phototoxic reaction?

As we mentioned before, a phototoxic reaction is a type of drug-induced photosensitivity reaction. Unlike a photoallergic reaction, as we’ll see later, in a phototoxic reaction, the immune system doesn’t play a part.

Phototoxic reactions represent 95% of all drug-induced photosensitivity reactions. They can develop a few minutes or hours after taking the drug and the main symptoms are as follows:

• Erythema and edema
• Itchy blisters
• Symptoms similar to severe sunburn

These reactions are more common with orally administered drugs and develop because they create free radicals that interact with oxygen, resulting in highly reactive and cell-damaging chemicals.

What is a photoallergic reaction?

This is another type of photosensitivity reaction. In this type of reaction, as noted above, the immune system is involved. To trigger a photoallergic reaction, UV rays have to cause a chemical transformation to the administered drug.

The drug is transformed into another chemical called hapten, which interacts with skin proteins and eventually triggers an immune reaction.

Among the most common symptoms, there’s eczematous inflammation if you took the medicine orally or a rash in the case where it has been administered topically.

What are the drugs that can cause photosensitivity reactions?

Many medications can have this type of reaction. Therefore, you should always check the technical specifications of the drugs to know if they are photosensitive drugs or not.

However, we’ll provide a short list of some of these medications. Of course, remember that there are many more, so you should always consult your doctor or the pharmacist.

• Antimicrobials such as tetracyclines, cephalosporins, or tuberculosis medications
• Cardiovascular drugs: thiazides, ACE inhibitors, or statins
• Hypoglycemic drugs, which are drugs that reduce glucose levels
• NSAIDs or non-steroidal anti-inflammatory drugs
• Retinoids
• Psychotropic drugs
• Chemotherapeutic agents
• Antihistamines

Learning about medications is key

It’s essential to be informed about the side effects that medications can cause. To do this, you can read both the package leaflet and the technical sheet and consult your doctor. Indeed, drug-induced photosensitivity reactions are common, and knowing your triggers is very important to prevent them.