ConditionSkin, hair & nails
Chronic Actinic Dermatitis
Chronic actinic dermatitis (CAD) is a rare, long-lasting skin condition in which the skin becomes abnormally sensitive to sunlight and reacts with an itchy, thickened, eczema-like rash on sun-exposed areas: the face, back of the neck, scalp, V of the chest and backs of the hands. It mostly affects men over 50 who spend time outdoors, and many also have contact allergies. Strict light protection, avoiding contact allergens and anti-inflammatory treatment control most cases.
Also called: CAD, photosensitivity dermatitis, actinic reticuloid, persistent light reaction, photosensitive eczema
At a glance
- What it is
- A chronic eczema-like reaction of skin to UV and sometimes visible light.
- Who gets it
- Mainly men over 50, often outdoor workers or gardeners. Can occur in people with atopic eczema and HIV.
- Where
- Face, ears, scalp, back and sides of the neck, V of the chest, backs of hands, with a sharp cut-off at clothing lines.
- Diagnosis
- Phototesting and patch and photopatch testing by a dermatologist.
- Treatment
- Strict sun and light protection, avoiding contact allergens, steroid or calcineurin creams, and immunosuppressants for severe cases.
When to get help
See a doctor within a day or two
- Rapidly spreading red rash over most of the body (erythroderma), with chills or feeling unwell
- Oozing, crusted, painful areas that may be infected
Book a routine appointment
- An itchy rash on the face, neck and hands that worsens after sun exposure and persists for weeks
- A rash that flares even through car or house windows, or under indoor lights
- Thickened, leathery skin on sun-exposed areas
- A new photosensitive rash after starting a medicine
Usually safe to manage at home
- Known chronic actinic dermatitis that is stable on your treatment plan, with consistent light protection
What happens in chronic actinic dermatitis
In CAD, the immune system reacts to sun-exposed skin as if it were an allergen. UV radiation is thought to alter proteins in the skin, which then trigger a delayed (type IV) allergic reaction, similar to allergic contact dermatitis but triggered by light.
Most people react to UVB, many also to UVA, and some even to visible light. Severe cases can flare through window glass or under fluorescent lighting.
Risk factors
- male sex and age over 50
- outdoor work or hobbies such as gardening and golf
- contact allergies to plants (Compositae family, such as chrysanthemums and ragweed), fragrances and sunscreen ingredients
- existing atopic eczema, or allergic contact dermatitis that has become light-sensitive
- HIV infection
- darker skin types are also affected and may be underdiagnosed
Symptoms
- intensely itchy, red, scaly patches on sun-exposed skin
- thickened, leathery skin (lichenification) with exaggerated skin lines
- patchy darkening or lightening of the skin
- a sharp cut-off at the collar, sleeves and hat line
- typical sparing of the upper eyelids, the skin behind the ears, under the chin and in deep skin folds
- worse in spring and summer, but often persistent through winter
- loss of eyebrows and scalp hair from scratching in severe cases
In severe cases the rash can spread to covered skin and become widespread.
Conditions that look similar
| Condition | Key differences |
|---|---|
| Airborne contact dermatitis | Also affects shaded areas such as upper eyelids and under the chin |
| Polymorphous light eruption | Comes and goes within days of sun exposure, mainly in younger women, in spring |
| Drug-induced photosensitivity | Starts after a new medicine, such as thiazides, doxycycline or NSAIDs |
| Atopic eczema | Lifelong history, affects skin folds |
| Cutaneous T-cell lymphoma | Rare, can mimic severe CAD (the old term "actinic reticuloid" described this look). Biopsy distinguishes |
| Lupus | Light-sensitive rash with other systemic features, positive antibodies |
Diagnosis
A dermatologist with expertise in photodermatology will perform:
- Phototesting: small areas of skin on the back are exposed to measured doses of UVB, UVA and visible light. People with CAD burn or react at abnormally low doses
- Patch testing: to identify contact allergens, which are present in many patients
- Photopatch testing: patch tests exposed to UVA to detect photoallergens, including sunscreen chemicals
- Skin biopsy: sometimes, to exclude lymphoma
- Blood tests: to exclude lupus and porphyria in some cases
Treatment
Light protection
This is the foundation:
- avoid going out in the middle of the day, especially from spring to autumn
- wear a broad-brimmed hat, long sleeves, high collars and gloves
- use high-factor (SPF 50+), broad-spectrum sunscreens that protect against UVA, choosing ones free of your contact allergens. Tinted mineral sunscreens with iron oxides help against visible light
- apply UV-filtering film to car and home windows
- some people need to reduce exposure to fluorescent lighting
Avoid contact allergens
If patch tests show allergies, avoiding those substances (such as Compositae plants, fragrances or specific sunscreen chemicals) is essential and can greatly improve control.
Medicines
- topical corticosteroids for flares
- tacrolimus or pimecrolimus ointment for the face and long-term use, without steroid side effects
- emollients to support the skin barrier
- oral antihistamines for sleep
- systemic treatments for severe disease: short courses of oral steroids, azathioprine, mycophenolate, cyclosporine or methotrexate, and in some cases dupilumab
- carefully supervised low-dose phototherapy (desensitization) under steroid cover, in specialist centers
Outlook
CAD is chronic, often lasting many years. With rigorous light protection and treatment, symptoms improve in most people, and some gradually lose their sensitivity over 10 or more years. Reduced quality of life from restrictions on outdoor activity is common, and support from a dermatology team helps.
Frequently asked questions
What is chronic actinic dermatitis?
It is a rare, long-term condition in which sunlight, and sometimes indoor light, triggers an itchy, thickened eczema-like rash on exposed skin. It mainly affects older men who spend time outdoors and is often linked with contact allergies.
What triggers chronic actinic dermatitis?
Ultraviolet light, especially UVB and UVA, triggers flares. In severe cases visible light can trigger it too. Contact allergens such as plant chemicals, fragrances and some sunscreen ingredients often worsen it.
How is chronic actinic dermatitis diagnosed?
A dermatologist uses phototesting, exposing small skin areas to measured light doses, together with patch and photopatch tests for contact allergies. A biopsy is sometimes done to rule out lymphoma, which can look similar.
Is chronic actinic dermatitis curable?
There is no quick cure, but it can be well controlled with strict light protection, allergen avoidance and anti-inflammatory treatment. Some people slowly become less sensitive over many years.
What sunscreen is best for chronic actinic dermatitis?
A broad-spectrum SPF 50+ sunscreen with strong UVA protection, free of your known contact allergens, is best. Tinted mineral sunscreens containing iron oxides also block visible light. Clothing and window films add protection.
Sources
This guide was written from current patient and clinical guidance, including:
- British Association of Dermatologists: Chronic actinic dermatitis patient information leaflet
- American Academy of Dermatology (AAD): Photosensitivity and sun allergy
- DermNet: Chronic actinic dermatitis
- British Photodermatology Group: Phototesting guidance
- MedlinePlus: Sun sensitivity