Diagnostic Problem-Solving

Diagnostic Problem-Solving:  

What's wrong with me?

An excess sensitivity to the sun or other forms of light is known as Photosensitivity.   A person may be sensitive to a specific type of radiation (UVA, or UVB) or to a broad range across the UV spectrum.   Sun sensitivity may appear as bad sunburn or rash, blisters, or sores.  Reaction usually occurs after a very short amount of exposure time. Some people experience an immediate reaction and others react after a delay.  Photosensitivity is an abnormal response of the skin to light exposure.  You get a reaction to sun or other sources of light, you react to sunlight in only a very short amount of time, or your reactions are extreme for the amount of sun exposure.  You can be extra sensitive to the sun for a number of reasons including a disease, genetics, a photosensitive drug you are taking, or something in your environment like certain citrus fruit or perfumes, and there are other reasons.  Sun sensitivity can be due to a primary medical condition, side effect from medication, or reaction ingredients in products. 

Other terms for sun sensitivity include: sun allergy, photoreaction, photoallergic, photosensitivity, phototoxic.  Diagnoses include photodermatoses of solar urticaria or sun hives, polymorphic light eruption, and actinic prurigo.  lupus and other auto-immune conditions, porphyria, polymorphic light eruption, and other light reactive conditions. 

Pictures of various light sensitive conditions

Search for your sun or light sensitivity condition by looking at a variety of pictures.

Dermatology Image Atlas - John Hopkins University  http://dermatlas.med.jhmi.edu/derm/

What are the most frequent diagnostic categories of photosensitivity disorders?

It can be challenging to differentiate among diagnostic categories.    Symptoms can look very similar.   Conditions can coexist in one individual.    Symptoms can vary widely between persons and within an individual over time.   Exposure time necessary to provoke symptoms can vary over time and correlate to seasonal environmental changes and geographic location.
(percent of total: a study of 203 people, 63% women with mean age of 50 years)
  • 26% Polymorphous light eruption
  • 17% Chronic actinic dermatitis
  •   8% Photoallergic contact dermatitis
  •   7% Systemic phototoxicity to therapeutic agents
  •   4% Solar urticaria

Positive Photopatch Test Reactions
·      sunscreens
·      fragrances
·      antimicrobial agents

1.     J Am Acad Dermatol. 1995 Oct;33(4):597-602. Results of evaluation of 203 patients for photosensitivity in a 7.3-year period. Fotiades J, Soter NA, Lim HW.
2.     Arch Dermatol.  2003 Sept; 139:1149-1154. Characteristics and Prognosis of Idiopathic Solar Urticaria.  Beattie PE, Dawe RS, Ibbotson SH, Ferguson J.

Table 1. Classification of sun related skin conditions (photodermatoses)[NationalSkin Center]

Drug photosensitivity:
Systemic phototoxicity (caused by ingesting something)
Systemic photoallergy (caused by ingesting something)
Phototoxic contact dermatitis (something contacts the skin)
Photoallergic contact dermatitis (something contacts the skin)
Photo-aggravated skin conditions
Endogenous eczema
Collagen vascular disease
Idiopathic acquired photodermatoses
(Sun related skin conditions from an unknown cause)
Polymorphic light eruption
Actinic prurigo
Hydroa vacciniforme
Solar urticaria
Chronic actinic dermatitis
Genetic & Metabolic disorders
o Xeroderma pigmentosum
o Cockayne's syndrome
o Bloom's syndrome
Nutrional deficiencies
o Pellagra
o Hartnup disease [Kwok]

Diagnostic Overview

Chemical photosensitivity can either be from ingesting something (drugs, food, liquids), or from being in contact with something on the skin (topical) like plants, liquids, skin products, perfumes, etc.

Photosensitivity reactions from skin contact result in patterns of where the substance contacted the skin and the substance was exposed to sunlight. The result can be bizarre patterns such as dot patterns from a weed whip or odd blotches from spilling lime juice.

Photosensitivity related to plants is called phytophotodermatitus.

Reactions from chemical photosensitivity from ingesting something are usually confined to sun exposed skin.

Chemical photosensitivity can result in phototoxic or photoallergic reactions.

Idiopathic acquired photodermatoses are sun related skin conditions from an unknown cause and include solar urticaria, polymorphous light eruption and others.1

Genetic and metabolic disorders include porphyrias, xeroderma pigmentosum, Cockayne's syndrome, and Bloom's syndrome.    Nutrional deficiencies include pellagra and Hartnup disease.1

Diseases that may be aggravated by sunlight include lupus erythematosus, acne vulgaris, Dariers disease, Grovers disease and herpes simplex.6

 A Starting Point

The diagnostic chart (below) can be used to help figure out what is wrong.   People who have photosensitivity might use this information as a starting point for a discussion with your physician to determine appropriate diagnostic tools for you.   Sometimes, a physician will appreciate a list to spark the thinking process.  Talk to your doctor to determine what kind of sun sensitive condition that you have.

The diagnostic chart in Table 2 is created from several sources.   Links to images or pictures of the skin condition are used in addition to the diagnostic chart.   Links to medical descriptions of the photosensitive condition are also in the diagnostic chart to assist diagnosing photosensitivity.

Table 2: Diagnostic Chart for Sun Sensitive Conditions

Reaction type
Occurs within ? after exposure
Time for reaction to go away
Area affected 
Other clues (usually)
Age usually discovered, usually found in male/female 
Normal sunburn
sunburn reaction
30 minutes to 4 hours after exposure3
peaks at 24 hours and lasts up to 72 hours. Skin peels 2 to 7 days later.3
exposed skin
severe cases have swelling and blistering.

Chemical photosensitivity (contact or ingested)

Contact photosensitivity from something in contact with the skin
either phototoxic or photoallergic reaction (see below)

Usually exposed skin with exposure to both contact item and the sun. 
Consider airborne  like sawdust, and topicals like plants,  sunscreens, perfumes,  cosmetic & bath products.4

Chemical  photosensitivity phototoxic, 
 Exaggerated sunburn reaction after only a short exposure (ingested or contact)
within hours of exposure

Exposed skin
List of drugs,
List of drugs, recent drug ingestion, or applied to skin. Also ingested items like quinine.
Any age
Chemical photosensitivity photoallergy,
 Images, eczema, rash  (ingested or contact)
24 to 48 hours after exposure

First, exposed skin, may later spread to non-exposed areas.
List of drugs
List of drugs, recent drug ingestion, or applied to skin. Also ingested items like quinine.
Any age
Phytophotodermatitis (plants),
Images, Redness and blisters, changes in pigment in odd, bizarre shapes  such as linear streaks3

Hyperpigmentation can last for months.3
Skin exposed to plant and sun. Common plants: celery family, certain grasses, carrots, limes, citrus, daisy family.3
Exposure to plants in spring and summer.3

Idiopathic acquired photodermatoses1
(Sun related skin conditions from an unknown cause)
Reaction type
Occurs within ? after exposure
Time for reaction to go away
Area affected 
Other clues (usually)
Age usually discovered, usually found in male/female 
Solar urticaria, 
Images, rash, hives (urticaria) , swelling (angioedema)
within 30 minutes of exposure
Exposed skin
 Sunlight, through glass, fluorescent lighting can cause reactions. 4

Chronic actinic dermatitis (actinic reticuloid), photosensitivity dermatitus4 Persistent light reaction, 
Images, lichenified plaques, chronic eczematous pattern of photosensitivity4
months, worst, in summer, can persist all year.4
Initially affects exposed skin, but spreads to  non-exposed skin4
Often follows years of  contact allergies. Sunlight, through glass, fluorescent lighting can cause reactions4
typically older men4
Actinic prurigo, Hutchinson’s summer prurigo
itchy, acute facial or forearm dermatitis with edematous papules and vesicles which progress to crusting and epidermal thickening3

face, forearms, both exposed & non-exposed skin
occurs in spring, annually
North and South American Indians, female/male: 2:1 mostly before adulthood2
Polymorphic light eruption (PMLE), 
Images, Thought to be sunburn or prickly heat4, discrete erythematous papules or plaques
new lesions appear within hours or days of sun exposure
remain 1 to 7 days, heals without scarring2
exposed skin, but not all exposed skin
occurs in spring, some improve through summer, some get worse4
onset of disease is sudden, later childhood before age 303, mostly female2 Up to 30% in women using tanning beds4
Hereditary polymorphic light eruption
see above

see above

family history
North and South American Indians,
Juvenile spring eruption,  (PMLE related)
Images, 2  to 3 mm discrete papules or vesicles on ears and cheeks3 Tiny blister on rims of ears4

lasts 1 or 2 weeks, then reappears next spring3

22% will go on to develop PMLE3
fair skinned boys, 5 to 12 years old3
Hydroa vacciniforme,  (PMLE related)
Images, images2, a few discrete, deep-seated vesicles/papules on photoexposed areas of face, hands and forearms4,

Can last up to 4 weeks. Heal with scarring.3
More episodes with  sun exposure3
Rarely the eye is involved. Rarest form of PMLE3

Genetic disorders7
Reaction type
Occurs within ? after exposure
Time for reaction to go away
Area affected 
Other clues (usually)
Age usually discovered, usually found in male/female 
Xeroderma pigmentosum, 
Images, prolonged sunburn, numerous freckles, skin dryness, photophobia3,4

sunburn which takes weeks to go away3
tumors, skin cancer4
family history, Onset of skin lesions by 18 months.3
infancy, childhood
Cockayne's syndrome

family history
Bloom's syndrome

family history
Rothmund Thompson syndrome

Ataxia telangiectasia


Metabolic disorders7
Reaction type
Occurs within ? after exposure
Time for reaction to go away
Area affected 
Other clues (usually)
Age usually discovered, usually found in male/female 

family history

Erythropoietic protoporphyria, 
Images, intense burning pain, no visible skin rash
pain within minutes of sun exposure3

Intense sun may result in facial edema, erythema, or urticaria3.
family history, inherited disorder of porphyrin metabolism3
infancy, childhood
porphyria cutanea tarda  (PCT), 
Images, blisters4

typically adults rather than children4
Hartnup disease



Nutritional disorders7
Reaction type
Occurs within ? after exposure
Time for reaction to go away
Area affected 
Other clues (usually)
Age usually discovered, usually found in male/female 

Collagen vascular disorders7
Reaction type
Occurs within ? after exposure
Time for reaction to go away
Area affected 
Other clues (usually)
Age usually discovered, usually found in male/female 
Lupus Erythematosus, discoid, 
Images,  lesions with  erythematous papule or plaque some scaling, malar rash5

eruption occurs 1 to 7 days after exposure3
mostly exposed skin

2:1 female to male, most often ages 20 to 405

infancy, childhood

1[Kwok] Evaluation of A Photosensitive Rash, DR Colin Kwok, NSC Bulletin For Medical Practitioners -> Vol 11 No 1, 2000, National Skin Centre [National Skin Center]
3Chapter 10, Sun Sensitivity. Color Textbook of Pediatric Dermatology, 3rd edition, By William L. Weston, MD; Joseph G. Morelli, MD; and Alfred Lane, MD, ISBN 0323018211 · Published April 2002
4Chapter 28 Photodermatology and Photodermatoses, Diseases of the Skin, Gary M. White & Neil H. Cox, 2002, W. B. Saunders. White
5eMedicine - Lupus Erythematosus, Discoid Article by Jeffrey P Callen, MD
6Photosensitivity, by David R. Bickers, MD, Best Practice of Medicine. March 2000.
7 Inamadar AC, Palit A. Photosensitivity in children: An approach to diagnosis and management. Indian J Dermatol Venereol Leprol 2005;71:73-79. from: http://www.ijdvl.com/article.asp?issn=0378-6323;year=2005;volume=71;issue=2;spage=73;epage=79;aulast=Inamadar


Consult with your physician regarding any treatments or medical advice suggested by this website.

We are not physicians, we are people trying to learn about our conditions and better our lives. We try to be accurate, but the articles and advice may have errors, become out-of-date, or even give bad advice. 

We highly recommend that you try anything new in moderation, to test for any reaction you might have.

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