eMedicine Specialties > Dermatology > Allergy & Immunology

Urticaria, Solar: Differential Diagnoses & Workup

Author: Elma D Baron, MD, Assistant Professor of Dermatology, Case Western Reserve University, University Hospitals of Cleveland; Director of Skin Study Center, University Hospitals Research Institute; Acting Chief of Dermatology, Veterans Affairs Medical Center, Cleveland
Coauthor(s): Charles R Taylor, MD, Assistant Professor of Dermatology, Harvard Medical School; Director of Phototherapy Unit, Department of Dermatology, Massachusetts General Hospital
Contributor Information and Disclosures

Updated: Mar 29, 2007

Differential Diagnoses

Berloque Dermatitis
Urticaria, Acute
Drug-Induced Photosensitivity
Urticaria, Cholinergic
Erythropoietic Protoporphyria
Lupus Erythematosus, Acute
Polymorphous Light Eruption

Other Problems to Be Considered

  • Polymorphous light eruption is much more common than solar urticaria and may affect the same sites, but the lesions do not subside as quickly upon cessation of sun exposure.
  • Erythropoietic protoporphyria usually manifests earlier in life.
  • Lupus erythematosus is more common in women, and signs and symptoms, other than dermatologic ones, accompany the acute systemic form. Localized cutaneous forms have different morphologies (eg, discoid, papulosquamous, annular); however, lupus erythematosus should be excluded through laboratory test findings.
  • Photocontact dermatitis manifests in a pattern suggestive of the contactant or allergen and does not totally disappear upon discontinuation of sun exposure.
  • Miliaria rubra (heat rash) can be mistaken for solaria urticaria.
  • Churg Strauss syndrome may manifest solar urticaria.

Workup

Laboratory Studies

  • Perform serologic tests for antinuclear antibody, Ro, and La antibodies to exclude connective-tissue disease (eg, lupus erythematosus).
  • Perform testing to exclude metabolic causes (eg, porphyrias).
    • Evaluate the plasma porphyrin level.
    • If abnormal results are found, follow with a quantitative 24-hour urinary and fecal porphyrin measurement, as well as erythrocyte porphyrin determination.

Other Tests

  • Phototesting confirms the diagnosis, identifies the action spectrum, and establishes baseline data (eg, minimum urticarial dose [MUD]) for possible therapeutic interventions and monitoring in the future.
    • Solar urticaria has a wide action spectrum. Perform phototesting using broadband UV-B (290-320 nm), UV-A (320-400 nm), and visible light sources (400-800 nm). Most patients with solar urticaria have provocative wavelengths in the UV-A and visible ranges, especially green or blue.
    • Duration of exposure under visible light should be less than an hour. Typically, the light emitted by a slide projector is used. Measures must be taken to avoid excessive heat output from the light source in order to eliminate the possibility of cholinergic- or heat-induced urticaria, instead of actual solar urticaria. A water filter may be placed in front of the light source to absorb excess heat.
    • Phototesting with narrowband UV-B (311-313 nm) is recommended if therapy with this light source is being considered. Occasionally, these tests do not produce the expected reaction.
    • Phototesting with other light sources (eg, solar simulators, lasers) may be necessary in difficult-to-establish cases.
    • Provocation with natural sunlight may be performed if ambient conditions allow.
    • Many patients with solar urticaria have an inhibition spectrum. If their skin is first exposed to wavelengths known to induce solar urticaria and is then immediately afterward, or possibly concurrently, exposed to radiation within the inhibition spectrum, the urticarial reaction is either eliminated or diminished.

Histologic Findings

Histologic changes are typically found in the dermis in the form of vasodilatation, increased permeability of the vascular endothelium, and edema. Eosinophil infiltration and deposition of eosinophil granule proteins in the dermis are prominent during early stages of the lesion. Neutrophils are found in increased numbers around the upper dermal vessels. Dermal mast cells may increase in number. After 24 hours, the dermal infiltrate is predominantly composed of mononuclear leukocytes.

More on Urticaria, Solar

Overview: Urticaria, Solar
Differential Diagnoses & Workup: Urticaria, Solar
Treatment & Medication: Urticaria, Solar
Follow-up: Urticaria, Solar
References
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References

  1. Collins P, Ahamat R, Green C, Ferguson J. Plasma exchange therapy for solar urticaria. Br J Dermatol. Jun 1996;134(6):1093-7. [Medline].

  2. Dawe RS, Ferguson J. Prolonged benefit following ultraviolet A phototherapy for solar urticaria. Br J Dermatol. Jul 1997;137(1):144-8. [Medline].

  3. Fotiades J, Soter NA, Lim HW. Results of evaluation of 203 patients for photosensitivity in a 7.3-year period. J Am Acad Dermatol. Oct 1995;33(4):597-602. [Medline].

  4. Fukunaga A, Horikawa T, Yamamoto A, Yamada Y, Nishigori C. The inhibition spectrum of solar urticaria suppresses the wheal-flare response following intradermal injection with photo-activated autologous serum but not with compound 48/80. Photodermatol Photoimmunol Photomed. Jun 2006;22(3):129-32. [Medline].

  5. Harris A, Burge SM, George SA. Solar urticaria in an infant. Br J Dermatol. Jan 1997;136(1):105-7. [Medline].

  6. Khoo SW, Tay YK, Tham SN. Photodermatoses in a Singapore skin referral centre. Clin Exp Dermatol. Jul 1996;21(4):263-8. [Medline].

  7. Miyauchi H, Horio T. Detection of action, inhibition and augmentation spectra in solar urticaria. Dermatology. 1995;191(4):286-91. [Medline].

  8. Roelandts R, Ryckaert S. Solar urticaria: the annoying photodermatosis. Int J Dermatol. Jun 1999;38(6):411-8. [Medline].

  9. Roelandts R. Diagnosis and treatment of solar urticaria. Dermatol Ther. 2003;16(1):52-6. [Medline].

  10. Ryckaert S, Roelandts R. Solar urticaria. A report of 25 cases and difficulties in phototesting. Arch Dermatol. Jan 1998;134(1):71-4. [Medline].

  11. Shimauchi T, Kabashima K, Tokura Y. Solar urticaria as a manifestation of Churg-Strauss syndrome. Clin Exp Dermatol. Mar 2007;32(2):209-10. [Medline].

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Further Reading

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Keywords

solar urticaria, sun hives, allergy, allergic reaction, anaphylaxis, anaphylactoid reaction, angioedema, photodermatosis, pruritus, solar irradiation, minimum urticarial dose, MUD, polymorphous light eruption, PMLE, erythropoietic protoporphyria, lupus erythematosus, photocontact dermatitis, miliaria rubra, psoralen–UV-A, PUVA, phototherapy, UV-A, broadband UV-B, narrowband UV-B, photochemotherapy, methoxsalen

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Contributor Information and Disclosures

Author

Elma D Baron, MD, Assistant Professor of Dermatology, Case Western Reserve University, University Hospitals of Cleveland; Director of Skin Study Center, University Hospitals Research Institute; Acting Chief of Dermatology, Veterans Affairs Medical Center, Cleveland
Elma D Baron, MD is a member of the following medical societies: American Academy of Dermatology, American Society for Photobiology, Photomedicine Society, and Society for Investigative Dermatology
Disclosure: Nothing to disclose.

Coauthor(s)

Charles R Taylor, MD, Assistant Professor of Dermatology, Harvard Medical School; Director of Phototherapy Unit, Department of Dermatology, Massachusetts General Hospital
Charles R Taylor, MD is a member of the following medical societies: American Academy of Dermatology, American Medical Association, American Society for Laser Medicine and Surgery, Massachusetts Medical Society, and Society for Investigative Dermatology
Disclosure: Nothing to disclose.

Medical Editor

Donald Belsito, MD, Clinical Professor, Department of Internal Medicine, Division of Dermatology, University of Missouri at Kansas City; Private Practice, American Dermatology Associates, LLC
Donald Belsito, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Contact Dermatitis Society, Dermatology Foundation, Kansas Medical Society, Noah Worcester Dermatological Society, Phi Beta Kappa, and Phi Beta Kappa
Disclosure: Nothing to disclose.

Pharmacy Editor

Michael J Wells, MD, Associate Professor, Department of Dermatology, Texas Tech University Health Sciences Center
Michael J Wells, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, and Texas Medical Association
Disclosure: Nothing to disclose.

Managing Editor

Jeffrey Meffert, MD, Assistant Clinical Professor of Dermatology, University of Texas Health Science Center-San Antonio
Jeffrey Meffert, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

CME Editor

Joel M Gelfand, MD, MSCE, Medical Director, Clinical Studies Unit, Assistant Professor, Department of Dermatology, Associate Scholar, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania
Joel M Gelfand, MD, MSCE is a member of the following medical societies: Society for Investigative Dermatology
Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

 
 
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