Phototherapy Side Effects in Eczema: What to Expect and How to Stay Safe

When eczema is severe or won’t respond to creams, phototherapy (medical light treatment, often narrowband UVB) can be a game‑changer. But it’s normal to worry about side effects before committing to multiple sessions a week under ultraviolet light.

This guide walks through the most common and important side effects so you can weigh benefits and risks with your dermatologist.

Common Short‑Term Side Effects

Most side effects during treatment are mild and manageable:

• Skin redness and sunburn‑like irritation
  After a session, skin can feel warm, tight, or look pink to red, especially in sensitive areas like the neck or inner arms. This usually settles within 24–48 hours. Doses are typically adjusted if you burn easily.

• Dryness and itching
  UV light can temporarily increase dryness, even while it’s helping long‑term inflammation. Dermatologists often recommend liberal use of thick moisturizers and sometimes adjusting the timing of emollients around sessions.

• Stinging of active eczema patches
  Areas already inflamed may sting or feel more irritated immediately after exposure. This is usually short‑lived but worth reporting so your treatment plan can be tweaked.

• Temporary darkening or lightening of skin
  Some people notice patchy hyperpigmentation (darker areas) or, less often, lighter spots where eczema was most active. These changes often fade gradually once treatment is reduced or stopped but can last for weeks or months.

Less Common but Important Risks

These side effects are less frequent but matter for long‑term decisions:

• Blistering burns
  If the UV dose is too high for your skin type, blisters or severe burns can appear. Modern phototherapy units (for example, narrowband UVB cabins and excimer devices) are designed to minimize this, but you should report intense pain, swelling, or blisters immediately.

• Eye damage if unprotected
  UV light can injure the eyes, increasing risk of cataracts and irritation. Proper goggles or eye shields are non‑negotiable for every session. If your eyelids are being treated, this is done under controlled conditions.

• Photosensitivity reactions
  Certain medications (like some antibiotics, acne medicines, or diuretics) and medical conditions make skin more sensitive to UV. This can cause exaggerated burns or rashes. A full medication review with your dermatologist before starting is essential.

• Long‑term skin aging
  With many cumulative sessions, UV exposure can contribute to premature wrinkles, sun spots, and texture changes. This risk is typically higher with UVA or PUVA than with narrowband UVB, but it’s part of the long‑term equation.

• Skin cancer risk over time
  Repeated ultraviolet exposure may increase the risk of non‑melanoma skin cancers and possibly melanoma over many years. The level of risk depends on the type of phototherapy, total number of treatments, skin type, and personal or family history of skin cancer. This is why dermatologists track the number of sessions and use the lowest effective dose.

How to Lower Your Risk During Phototherapy

You can play an active role in making treatment safer:

• Follow dosing and schedule exactly as directed; do not add tanning beds or extra sun exposure.
• Protect non‑treated areas with clothing or sunscreen if recommended.
• Moisturize regularly to combat dryness and support the skin barrier.
• Report new moles, changing spots, severe burns, or eye symptoms promptly.
• Keep a running list of all medications and supplements and update your dermatologist if anything changes.

Deciding Whether Phototherapy Is Right for You

For many people with moderate to severe eczema, the relief from itching, sleep disruption, and flares outweighs the manageable side effects, especially when other treatments haven’t worked. A careful discussion with your dermatologist about your skin type, medical history, and lifestyle will help clarify:

• Which type of phototherapy is safest for you
• How long a course is likely to last
• How your long‑term skin cancer risk will be monitored

Understanding the potential side effects upfront lets you start phototherapy informed, prepared, and better able to notice problems early—so you can get the benefits of treatment while protecting your skin for the long run.