What Is Sun Allergy?

Introduction

Sun allergy, medically known as photosensitivity or photodermatitis, is a condition that affects individuals when their skin reacts abnormally to sunlight exposure.¹ While the sun is a vital source of energy and vitamin D, some people experience adverse reactions when their skin is exposed to sunlight. In this comprehensive guide, we will explore the various facets of sun allergies, including the different types, their mechanisms, symptoms, diagnosis, prevention methods, available treatments, and how to effectively manage life with this condition.

Sun allergies are more common than you might think, and understanding them is crucial for anyone who spends time outdoors. Whether you're planning a beach vacation, enjoying outdoor activities, or simply stepping outside on a sunny day, knowing about sun allergies can help you protect your skin and overall health. So, let's dive into this informative journey to unravel the mysteries of sun allergies and how to deal with them effectively.

Types of sun allergies

Sun allergies encompass several distinct conditions, each with its own set of characteristics and triggers. Understanding these types is essential for proper diagnosis and management. Here, we'll delve into the primary categories of sun allergies:²

Polymorphic light eruption 

Polymorphic light eruption, often abbreviated as PLE, is one of the most common forms of sun allergy. It typically occurs within hours to days after exposure to sunlight, particularly in the spring and early summer when the skin is not acclimated to ultraviolet (UV) radiation. Symptoms of PLE may include an itchy or burning rash, small red bumps, or raised patches on the skin.

Solar urticaria

Solar urticaria is characterised by hives or welts that develop rapidly on the skin upon sun exposure. These hives can be intensely itchy and appear as raised reddish or skin-coloured bumps. Solar urticaria is considered a rare form of sun allergy and can occur within minutes of exposure to sunlight. It can affect any part of the body that is exposed to the sun.

Photoallergic dermatitis

Photoallergic dermatitis is a sun allergy triggered by specific substances applied to the skin, such as certain fragrances or medications, which become allergenic when exposed to UV radiation.

This condition results in an itchy rash that may resemble eczema or contact dermatitis. It typically occurs in areas where the substance was applied, making it different from other sun allergies that affect exposed skin.

Understanding the mechanism

To comprehend sun allergies fully, it's crucial to grasp the underlying mechanisms that lead to these adverse skin reactions. This section will shed light on how sun allergies develop and the pivotal role played by UV radiation and the immune system response. 

How do sun allergies develop?

Sun allergies originate from an abnormal response of the skin to UV radiation from the sun or artificial sources like tanning beds.³ While the exact causes can vary depending on the type of sun allergy, the common factor is the body's inability to tolerate UV exposure.

In many cases, it's not just the UV radiation itself that triggers the reaction but a combination of UV exposure and specific factors, such as genetic predisposition or the presence of photosensitising substances on the skin. 

Role of ultraviolet radiation

Ultraviolet radiation from the sun falls into three main categories: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC). As UVA and UVB are usually responsible for triggering sun allergies, they are discussed below.

Ultraviolet A radiation

UVA rays penetrate deep into the skin and are primarily responsible for premature ageing and wrinkling. It can also trigger or exacerbate certain sun allergies, especially photoallergic dermatitis.

Ultraviolet B radiation

UVB rays primarily affect the outer layers of the skin and are a key player in causing sunburn. Many sun allergies, including PLE and solar urticaria, are triggered by UVB exposure. 

Immune system response

The immune system plays a significant role in the development of sun allergies. When UV radiation interacts with the skin, it can trigger an immune response. In individuals with sun allergies, this response becomes hypersensitive, leading to the release of inflammatory substances and characteristic symptoms like rashes, itching, and hives.

Symptoms

Recognising the symptoms of sun allergies is essential for early identification and prompt management. Sun allergies often manifest as skin reactions. These reactions can vary from person to person but commonly include:⁴

• Redness — The affected skin may become red or flushed.
• Rash — A rash characterised by small, itchy bumps or patches may develop.
• Swelling — Some individuals may experience localised swelling in response to sun exposure.
• Itching — Itching is a hallmark symptom of many sun allergies. The affected skin may be intensely itchy, leading to discomfort and a strong urge to scratch. Redness often accompanies itching and may range from mild to severe.
• Pain or Discomfort — In some cases, sun allergies can cause discomfort or a burning sensation in the affected area. This discomfort may be exacerbated by scratching.
• Hives (Urticaria) — Solar urticaria, in particular, is characterised by the rapid development of hives or welts upon sun exposure. These hives are typically raised, red, and itchy.
• Blisters — In severe cases of sun allergies, blisters may form on the skin. These blisters can be painful and may require medical attention.
• Scaling or peeling — After the initial reaction, the skin may begin to peel or scale as it heals. This can leave the affected area dry and flaky.

It's important to note that the severity of these symptoms can vary from mild to severe, depending on factors such as the individual's sensitivity to UV radiation and the specific type of sun allergy they have.⁵ Additionally, some people may experience a delayed onset of symptoms, making it essential to be vigilant and seek medical advice if you suspect a sun allergy.

Diagnosis

Accurate diagnosis is crucial in managing sun allergies effectively. Healthcare professionals employ a variety of methods to confirm the presence of a sun allergy and identify its specific type. In this section, we'll explore the diagnostic procedures used:⁴ 

Medical history

A thorough medical history is the first step in diagnosing a sun allergy. Your healthcare provider will inquire about your symptoms, when they first appeared, and whether they are associated with sun exposure. They will also ask about your medical history, including any previous skin conditions or allergies.

Physical examination

During a physical examination, the healthcare provider will closely examine the affected skin. They will look for characteristic signs of sun allergies, such as redness, rashes, hives, or blisters. The distribution and appearance of these skin changes can provide important clues about the type of sun allergy.

Photo testing

Phototesting involves exposing a small area of your skin to controlled amounts of UV radiation.⁶ This test helps determine your skin's sensitivity to UV rays and can differentiate between various sun allergies. It is particularly useful in diagnosing conditions like PLE and solar urticaria 

Allergy testing

In cases of photoallergic dermatitis, allergy testing may be necessary. This typically involves patch testing, where small amounts of potential allergens are applied to the skin and exposed to UV radiation. If a reaction occurs, it helps identify the specific substance causing the allergy.

Prevention of sun allergy

Preventing sun allergies involves taking proactive steps to minimise the risk of skin reactions when exposed to sunlight. While complete avoidance of the sun may not be practical, especially in daily life, there are several effective strategies you can employ to protect your skin and reduce the likelihood of sun allergy symptoms:⁷

Sunscreen and protective clothing

Broad-spectrum sunscreen — Choose a broad-spectrum sunscreen with a high SPF (Sun Protection Factor) that protects against both UVA and UVB rays. Apply it generously to all exposed skin, even on cloudy days. 

• UV-protective clothing — Consider wearing clothing designed to block UV radiation. Look for garments with a UPF (ultraviolet protection factor) rating for added protection.
• Wide-brimmed hats — A wide-brimmed hat can shield your face, neck, and ears from direct sunlight.
• Sunglasses — Protect your eyes from UV radiation by wearing sunglasses that offer adequate UV protection.

Avoiding peak sun hours

The sun's rays are strongest between 10 a.m. and 4 p.m. Try to limit your outdoor activities during these peak hours to reduce sun exposure. If you must be outdoors, seek shade whenever possible.

Gradual sun exposure

If you're prone to sun allergies, it's essential to build up your skin's tolerance to UV radiation gradually. Start with short periods of sun exposure and gradually increase the duration as your skin becomes more accustomed to sunlight.

Identify and avoid triggers

If you have photoallergic dermatitis, work with a healthcare provider to identify and avoid specific substances or products that trigger your sun allergy. This may involve reading ingredient labels and being cautious with skincare products and medications.

Stay hydrated

Proper hydration can help your skin remain healthy and less susceptible to sun damage. Drink plenty of water, especially when spending time in the sun. 

Treatment options

When preventive measures fail to provide adequate protection or if you experience a sun allergy reaction, there are various treatment options available to alleviate symptoms and manage the condition effectively. The choice of treatment often depends on the type and severity of the sun allergy. Here are some common treatments:⁷

Over-the-counter (OTC) medications

• Antihistamines — OTC antihistamines like cetirizine or loratadine can help relieve itching, redness, and hives associated with sun allergies. It's essential to follow the recommended dosages and consult a healthcare provider if symptoms persist.
• Topical corticosteroids — Over-the-counter creams or ointments containing low-potency corticosteroids can provide relief from skin inflammation and itching. These should be used under the guidance of a healthcare professional.

Prescription medications

In cases of severe or recurrent sun allergies, a healthcare provider may prescribe the following:⁸

• Topical steroids — Stronger topical corticosteroids may be prescribed for more severe skin reactions.
• Oral steroids — In severe cases, a short course of oral corticosteroids may be recommended to reduce inflammation and suppress the immune response.
• Immunosuppressive medications — In rare instances, especially for severe solar urticaria, medications that suppress the immune system's response to UV radiation may be prescribed.

Phototherapy

Phototherapy, or light therapy, involves controlled exposure to UV radiation under medical supervision. It can be used to desensitise the skin and reduce the severity of some sun allergies, particularly solar urticaria. This treatment is typically administered in a healthcare setting. 

Avoiding triggering substances

If you have photoallergic dermatitis, the primary treatment is to identify and avoid the specific substances or products that trigger your allergic reaction. Your healthcare provider can assist in this process and recommend alternative products.

Key takeaways

• Sun allergies come in various types, each with unique triggers and symptoms.
• Understanding how UV radiation and the immune system contribute to sun allergies is crucial.
• Diagnosis involves a medical history, examination, and sometimes specialised testing.
• Prevention, such as sunscreen use and protective clothing, is essential
• Treatment options vary based on the type and severity of the sun allergy

Summary

In this guide, we've explored sun allergies, their types, symptoms, diagnosis, prevention, and treatment. While living with a sun allergy can be challenging, understanding the condition is key to effective management.  Remember, seeking medical advice is essential for proper management. With knowledge and precautions, you can lead a fulfilling life despite having a sun allergy.