Woman touching her face with both hands.

Many commonly used, even over-the-counter, medications can cause your skin to become more sensitive to the sun than usual. Photosensitising agents can become reactive or cause allergic reactions when they interact with ultraviolet (UV) light. This article details the causes, symptoms and management of drug-induced photosensitivity reactions.

What is drug-induced sun sensitivity?

Drug-induced photosensitivity (or drug induced sun sensitivity) develops when a medicine, which does not normally cause sensitivity, undergoes photoactivation as it interacts with UV light when it enters the skin.

Chemicals that have planar, tricyclic, or polycyclic structures absorb ultraviolet light, and often these altered chemicals cause cutaneous manifestations (such as phototoxic or photoallergic reactions). As stopping these medications is not always possible, it is important to understand how to protect skin from sunlight.

Woman taking medication
Certain medications can increase the skin’s sensitivity to the sun.
Woman taking medication
Certain medications can increase the skin’s sensitivity to the sun.

What are the symptoms of photosensitive reactions?

The clinical features of drug-induced photosensitivity can vary, as the type of reaction, either phototoxic or photoallergic, depends on the type of photosensitising agent that caused the sensitivity reaction.

Talk to your doctor or pharmacist if you’re worried about any of your symptoms, especially if you suspect you have drug-induced photosensitivity, or are not sure if your medication/s can cause photosensitivity reactions.

What is the difference between phototoxic and photoallergic reactions?

The main difference is that photoallergic reactions occur when the immune system reacts to the photoactive chemical causing swelling and inflammation, while phototoxic reactions occur solely due to the photoactive chemical reacting directly with skin cell membranes and cellular DNA, and do not involve the immune system.

Photoallergic reactions therefore only require a small amount of the photoactive chemical to be present as the immune system is very sensitive, while phototoxic reactions require a larger amount of the photoactive chemical to be present (although phototoxic chemicals differ in toxicity, and therefore different amounts of each chemical are required to cause a reaction).

What are the visual differences of phototoxic reaction and photoallergic reactions?

While phototoxic and photoallergic reactions are caused by different types of photoactive chemicals that induce different biochemical reactions, it can still be hard to differentiate between them when examining a person with photosensitivity. The main visual difference between the two reactions is that phototoxic reactions tend to look like severe sunburn that is mainly restricted to sun-exposed skin, while photoallergic reactions look more like Atopic Dermatitis and the reaction can spread from sun-exposed skin to unexposed areas.

Close-up of skin with a photoallergic reaction
Photoallergic reactions look more like Atopic Dermatitis.
Close-up of skin with a photoallergic reaction
Photoallergic reactions look more like Atopic Dermatitis.

Phototoxic and Photoallergic Reactions – What is the difference?

Phototoxic Reaction

Photoallergic Reaction

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Development (pathogenesis) of phototoxic and photoallergic reactions

What causes drug-induced photosensitivity reactions?

Both systemic (oral) medications and topically applied compounds have the potential to cause photosensitivity reactions. It is therefore important to consider the possibility of photosensitivity when choosing a moisturiser or skin lotion. Some anti-inflammatory medications, or ‘painkillers’, such as ibuprofen can also cause photosensitivity. Other commonly used photoactive medications include antibiotics, non-steroidal anti-inflammatory drugs, diuretics, statins, retinoids and antifungals.

Woman’s shoulder back
Photosensitivity reactions may also result from topically applied compounds.
Woman’s shoulder back
Photosensitivity reactions may also result from topically applied compounds.

What medications have the potential to cause photosensitivity?

Many commonly used medications that can cause photosensitivity are included in the below table called Common Photosensitising Medications, however, this is not a complete list and there are many other medications that could potentially cause photosensitivity.

Common Photosensitising Medications

  • Anticonvulsants (Neuroleptics)
  • Antibiotics
  • Diuretics
  • Hypoglycaemics
  • Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
  • PDT Pro-Photosensitisers
  • Retinoids

If you are not sure if the medication/s you are using can cause photosensitivity, or you want general information about which medications can cause photosensitivity, please ask your doctor or pharmacist.

Management of photosensitive reactions

What is the best way to protect against photosensitivity, if you have to take a photoactive medication?

The wavelengths of light that are known to cause drug-induced photosensitivity reactions are UVA (320-400 nm) and UVB (290-320 nm) range. However, certain chemicals can react with sunlight in the visible range. Therefore, avoiding exposure to the sun is paramount.

Furthermore, protecting skin by clothes and using a sunscreen with an effective UVA/UVB filter with a high SPF (50+) will help protect against the photoactivation of  most photoactive medication you may need to take. 

Always follow the usage instructions on the sunscreen, especially with regards to frequency of application. Generally avoiding excessive exposure will also help to reduce the risk of drug-induced photosensitivity reactions. Read more about how to protect the face or on body.

Woman in hat
A combination of proper clothing and a sunscreen with a high SPF is recommended.
Woman applying sun screen her nose.
Sunscreens are essential protection
Woman in hat
A combination of proper clothing and a sunscreen with a high SPF is recommended.
Woman applying sun screen her nose.
Sunscreens are essential protection

If you are at all concerned, always consult a doctor or pharmacist.

Many commonly used, even over-the-counter, medications can cause your skin to become more sensitive to the sun than usual. Photosensitising agents can become reactive or cause allergic reactions when they interact with ultraviolet (UV) light. This article details the causes, symptoms and management of drug-induced photosensitivity reactions.

What is drug-induced sun sensitivity?

Drug-induced photosensitivity (or drug induced sun sensitivity) develops when a medicine, which does not normally cause sensitivity, undergoes photoactivation as it interacts with UV light when it enters the skin.

Chemicals that have planar, tricyclic, or polycyclic structures absorb ultraviolet light, and often these altered chemicals cause cutaneous manifestations (such as phototoxic or photoallergic reactions). As stopping these medications is not always possible, it is important to understand how to protect skin from sunlight.

Woman taking medication
Certain medications can increase the skin’s sensitivity to the sun.
Woman taking medication
Certain medications can increase the skin’s sensitivity to the sun.

What are the symptoms of photosensitive reactions?

The clinical features of drug-induced photosensitivity can vary, as the type of reaction, either phototoxic or photoallergic, depends on the type of photosensitising agent that caused the sensitivity reaction.

Talk to your doctor or pharmacist if you’re worried about any of your symptoms, especially if you suspect you have drug-induced photosensitivity, or are not sure if your medication/s can cause photosensitivity reactions.

What is the difference between phototoxic and photoallergic reactions?

The main difference is that photoallergic reactions occur when the immune system reacts to the photoactive chemical causing swelling and inflammation, while phototoxic reactions occur solely due to the photoactive chemical reacting directly with skin cell membranes and cellular DNA, and do not involve the immune system.

Photoallergic reactions therefore only require a small amount of the photoactive chemical to be present as the immune system is very sensitive, while phototoxic reactions require a larger amount of the photoactive chemical to be present (although phototoxic chemicals differ in toxicity, and therefore different amounts of each chemical are required to cause a reaction).

What are the visual differences of phototoxic reaction and photoallergic reactions?

While phototoxic and photoallergic reactions are caused by different types of photoactive chemicals that induce different biochemical reactions, it can still be hard to differentiate between them when examining a person with photosensitivity. The main visual difference between the two reactions is that phototoxic reactions tend to look like severe sunburn that is mainly restricted to sun-exposed skin, while photoallergic reactions look more like Atopic Dermatitis and the reaction can spread from sun-exposed skin to unexposed areas.

Close-up of skin with a photoallergic reaction
Photoallergic reactions look more like Atopic Dermatitis.
Close-up of skin with a photoallergic reaction
Photoallergic reactions look more like Atopic Dermatitis.

Phototoxic and Photoallergic Reactions – What is the difference?

Phototoxic Reaction

Photoallergic Reaction

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Exaggerated sunburn

Distribution
Sun-exposed skin only

Immunologically mediated
No

Incidence
High

More than one exposure to agent required
No

Quantity of agent required to induce photosensitivity
Large

Speed of reaction post exposure to photoactive agent and light
Minutes to hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Clinical characteristics
Dermatitis

Distribution
Mainly sun-exposed skin,  yet may spread to other areas that have not been exposed to the sun

Immunologically mediated
Yes; Type IV

Incidence
Low

More than one exposure to agent required
Yes

Quantity of agent required to induce photosensitivity
Small

Speed of reaction post exposure to photoactive agent and light
24-72 hours

Development (pathogenesis) of phototoxic and photoallergic reactions

What causes drug-induced photosensitivity reactions?

Both systemic (oral) medications and topically applied compounds have the potential to cause photosensitivity reactions. It is therefore important to consider the possibility of photosensitivity when choosing a moisturiser or skin lotion. Some anti-inflammatory medications, or ‘painkillers’, such as ibuprofen can also cause photosensitivity. Other commonly used photoactive medications include antibiotics, non-steroidal anti-inflammatory drugs, diuretics, statins, retinoids and antifungals.

Woman’s shoulder back
Photosensitivity reactions may also result from topically applied compounds.
Woman’s shoulder back
Photosensitivity reactions may also result from topically applied compounds.

What medications have the potential to cause photosensitivity?

Many commonly used medications that can cause photosensitivity are included in the below table called Common Photosensitising Medications, however, this is not a complete list and there are many other medications that could potentially cause photosensitivity.

Common Photosensitising Medications

  • Anticonvulsants (Neuroleptics)
  • Antibiotics
  • Diuretics
  • Hypoglycaemics
  • Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
  • PDT Pro-Photosensitisers
  • Retinoids

If you are not sure if the medication/s you are using can cause photosensitivity, or you want general information about which medications can cause photosensitivity, please ask your doctor or pharmacist.

Management of photosensitive reactions

What is the best way to protect against photosensitivity, if you have to take a photoactive medication?

The wavelengths of light that are known to cause drug-induced photosensitivity reactions are UVA (320-400 nm) and UVB (290-320 nm) range. However, certain chemicals can react with sunlight in the visible range. Therefore, avoiding exposure to the sun is paramount.

Furthermore, protecting skin by clothes and using a sunscreen with an effective UVA/UVB filter with a high SPF (50+) will help protect against the photoactivation of  most photoactive medication you may need to take. 

Always follow the usage instructions on the sunscreen, especially with regards to frequency of application. Generally avoiding excessive exposure will also help to reduce the risk of drug-induced photosensitivity reactions. Read more about how to protect the face or on body.

Woman in hat
A combination of proper clothing and a sunscreen with a high SPF is recommended.
Woman applying sun screen her nose.
Sunscreens are essential protection
Woman in hat
A combination of proper clothing and a sunscreen with a high SPF is recommended.
Woman applying sun screen her nose.
Sunscreens are essential protection

If you are at all concerned, always consult a doctor or pharmacist.