Basics
Description
Adverse or abnormal reaction of the skin to sunlight
Epidemiology
- Variable for each disorder
- Photosensitivities with onset in childhood include albinism, hydroa aestivale, hydroa vacciniforme, the porphyrias (e.g., erythropoietic, erythropoietic protoporphyria, hepatoerythropoietic), and genetic disorders (e.g., xeroderma pigmentosa, Hartnup disease, poikiloderma congenitale, Bloom syndrome, and Rothmund Thomson and Cockayne syndromes).
- Photosensitivities that occur frequently in adults but can occur in childhood are vitiligo, chemically induced photosensitivities, polymorphous light eruption, connective tissue disease, and pellagra.
Risk Factors
- Family history
- Disease
- Exposure to toxins
Genetics
- Genetic disorders include the porphyrias and others as previously listed:
- The various porphyrias have variable inheritance patterns, whereas most of the other genetic disorders are inherited in an autosomal recessive pattern.
- There is a positive familial history in many cases of polymorphous light eruption.
Pathophysiology
Findings are diverse for the different disorders and rarely diagnostic.
Etiology
- Combination of sunlight with some abnormality in the skin such as loss of pigment, a chemical agent, a metabolic product, another skin disorder, a genetic disease, or an unknown factor produces a cutaneous abnormality.
- Specific wavelengths of the radiant energy emitted by the sun and reaching the earth are usually responsible for each photosensitivity disorder, most commonly ultraviolet B (UVB, 290 " 320 nm), ultraviolet A (UVA, 320 " 400 nm), and visible light (400 " 800 nm).
Diagnosis
History
- Age of onset of rash
- Occurrence
- Season: spring and summer
- Relation to sun exposure: time frame, effect of sun through glass
- Oral medications
- May be related to oral contraceptives, tetracyclines (doxycycline in particular), sulfa drugs, iodines/bromides, or phenytoin
- New topical agents (e.g., perfumes, lemons, limes, sunscreens, etc.):
- Photosensitivity may occur on neck or places where agents were placed on skin.
- Rash
- Accentuation of the rash on the nose, cheeks, and forehead with sparing of the eyelids and the submental portion of the chin
- There is often a sharp cutoff in the nuchal area at the collar line.
Physical Exam
- Distribution
- Distribution of lesions is the main sign of photosensitivity reactions.
- Lesions are prominent on sun-exposed skin such as the face, pinnae of the ears, the V of the neck, the nuchal area, and the dorsa of the hands.
- Often, sparing of the philtrum, the area below the chin, the eyelids, and other covered areas is seen.
- In phytophotodermatitis, linear or bizarre shapes can occur, including, as an example, hand prints if a caregiver has been squeezing limes and then picks up a child and the child is then exposed to sunlight.
- Lesion characteristics
- Vary with the particular disease and can include the following:
- Papules
- Vesicles
- Plaques (polymorphous light eruption)
- Sunburn (chemical reaction to a systemic agent)
- Linear areas of hyperpigmentation (chemical reaction to a topical agent)
- Skin cancers (xeroderma pigmentosum)
- Vesicles (porphyria)
- In some cases, scarring can also be seen related to severe burns (porphyria).
Diagnostic Tests & Interpretation
- Phototesting
- Using an artificial source of light can confirm the presence of certain photosensitivities. Procedures are of 2 types:
- The 1st is exposure of skin to increasing doses of UVA and UVB to determine the erythema response (present at lower exposures than usual) and possibly reproduce lesions in certain diseases.
- The 2nd is photopatch testing in which photoallergic chemicals are applied under patches in duplicate, and 1 set is subsequently exposed to UVA. Patients who have photoallergic contact dermatitis develop a reaction under only the exposed patch of the agent causing the problem.
Lab
Initial Lab Tests
- Genetic tests (optional): Find labs that perform genetic tests at www.genetests.org and enter disease name:
- Cell culture: evaluates DNA repair for xeroderma pigmentosum or shows chromosomal breaks in Bloom disease
- Measurement of specific amino acid and indole excretion patterns in Hartnup disease
- Measurements of antinuclear antibodies are helpful in connective tissue diseases.
- Biochemical tests
- Helpful for the diagnosis of the porphyrias, with elevated levels of various porphyrins specific to each type in the urine, blood, or stool
- Screening for connective tissue diseases should be done where appropriate.
- Screening for niacin deficiency
Differential Diagnosis
- Photosensitivity resulting from pigment loss
- Idiopathic photosensitivity
- Polymorphous light eruption
- Solar urticaria
- Chemically induced reactions
- Topical agents
- Perfumes
- Plant-associated phytophotodermatitis (e.g., lemons, limes, celery, parsnips, carrots, dill, parsley, figs, meadow grass, giant hogweed, mangos, wheat, clover, cocklebur, buttercups, shepherds purse, and pigweed)
- Blankophors (e.g., optical brighteners in detergents)
- Sunscreens
- Topical retinoids (e.g., tretinoin, adapalene, tazarotene)
- Systemic agents
- Tetracyclines, sulfonamides, nalidixic acid, griseofulvin, phenothiazines, oral hypoglycemic agents, amiodarone, quinine, isoniazid, and thiazide diuretics
- Metabolic disorders
- Porphyrias: disorders of hemoglobin synthesis producing various porphyrins that are photosensitizers
- Genetic disorders: see "Genetics "
- Cutaneous diseases aggravated by sunlight
- Connective tissue diseases
Treatment
General Measures
- Protection against sun exposure
- Avoiding the sun, particularly between 10 a.m. and 3 p.m., and wearing protective clothing is important.
- Sunscreens are helpful for those sensitive to UVB.
- Sunscreens should be water resistant and reapplied q2h.
- Sun protection factor (SPF; ratio of minimal erythema dose of sunscreened skin to minimal erythema dose of unprotected skin) >30
- Sunscreens are less effective for blocking UVA and therefore less effective in helping patients with sensitivities to longer wavelengths.
- Sunscreens that contain both UVA- and UVB-blocking capabilities offer better protection than most. These include sunscreens containing avobenzone, titanium dioxide, and zinc oxide.
- Avobenzone has a relatively short lifespan but is now available in a chemically stabilized form known by the trade names Helioplex and Active Photobarrier Complex.
- Mexoryl is another long-acting broad-spectrum sunscreen that has especially good UVA protection.
- Opaque formulations such as zinc oxide and titanium dioxide block UV and visible light but may be less cosmetically appealing; however, new formulations made from microfine particles of titanium dioxide or zinc oxide make it more appealing.
- Patients with severe photosensitivities may have to avoid any significant light exposure.
- Most patients require chronic protection against sun exposure. However, the problem is generally more acute in spring and summer months.
- Removal of the offending agent is necessary in chemically induced photosensitivities:
- Any severe and acute eruptions may require a short course of oral prednisone.
- Antimalarial agents have been used for polymorphous light eruption, lupus erythematosus, solar urticaria, and porphyria cutanea tarda and require the experience of a specialist.
Issues for Referral
If possible, it is important to accurately document the specific wavelength of light and the degree of photosensitivity to accurately advise the patient. This requires phototesting by a specialist.
Ongoing Care
Follow-up Recommendations
Patient Monitoring
Skin exams for skin cancers routinely with frequency dependent on type of photosensitivity; for example, more monitoring for genetic causes such as xeroderma pigmentosa
Patient Education
Education regarding significance of using sunscreen
Prognosis
With the exception of chemically induced photosensitivities, most of the conditions are chronic.
Additional Reading
- Chantorn R, Lim HW, Shwayder TA. Photosensitivity disorders in children: part I. J Am Acad Dermatol. 2012;67(6):1093.e1 " 1093.e18. [View Abstract]
- Chantorn R, Lim HW, Shwayder TA. Photosensitivity disorders in children: part II. J Am Acad Dermatol. 2012;67(6):1113.e1 " 1113.e15. [View Abstract]
- Kuhn A, Ruland V, Bonsmann G. Photosensitivity, phototesting and photoprotection in cutaneous lupus erythematosus. Lupus. 2010;19(9):1036 " 1046. [View Abstract]
- Segal AR, Doherty KM, Leggott J, et al. Cutaneous reactions to drugs in children. Pediatrics. 2007;120(4):e1082 " e1096. [View Abstract]
- Ten Berge O, Sigurdsson V, Brijinzeel-Koomen CA, et al. Photosensitivity testing in children. J Am Acad Dermatol. 2010;63(6):1019 " 1025. [View Abstract]
Codes
ICD09
- 692.72 Acute dermatitis due to solar radiation
- 692.82 Dermatitis due to other radiation
ICD10
- L56.8 Oth acute skin changes due to ultraviolet radiation
- L59.8 Oth disrd of the skin, subcu related to radiation
SNOMED
- 90128006 photosensitivity (finding)
- 22649008 photodermatitis (disorder)
FAQ
- Q: What is the best sunscreen to use?
- A: It depends on your particular problem. If you are sensitive to UVB, use a sunscreen with the highest SPF. If you are sensitive to UVA, sunscreens containing avobenzone, titanium dioxide, or zinc oxide are best.
- Q: I have heard that sunscreens with an SPF >15 are not necessary. Is this true?
- A: This is definitely not true for patients with photosensitivities who have abnormal responses to light and require excessive protection. Even for the healthy person, it is often not true. An SPF of 15 suggests that someone may receive 15 times more sun exposure with the sunscreen applied than without and not become sunburned. Some physicians have suggested that this is more than anyone should need. However, this number is calculated by testing in a controlled laboratory. Normal outdoor conditions, such as wind, reflection from water and sand, perspiration, and water exposure can significantly decrease the effectiveness of the sunscreen.
- Q: What is "sun allergy " ?
- A: This is a lay term for polymorphous light eruption, one of the most common photosensitivities, presenting with papules, vesicles, and plaques 1 " 2 days after sun exposure. It usually recurs every spring, and most patients learn to avoid sun exposure. However, ironically, it can improve with slow, gradual sun exposure.
- Q: Can I become allergic to sunscreens?
- A: Certain active agents in sunscreens can produce an allergic response in rare individuals. If the rash recurs with each use, switch to another sunscreen with different ingredients. If the problem continues, consult a specialist for evaluation.