Health Effects of Artificial Light
5. What are the effects on people who have conditions that make them sensitive to light?
- 5.1 Skin diseases
- 5.2 Eye conditions
- 5.3 Other conditions linked to light flicker
5.1 Skin diseases
LEDs do not emit UV
There are two groups of patients who react abnormally to
light: those whose diseases are induced by UV/IR or
visible light (the
photodermatoses) and those who have a pre-existing skin
condition which is made worse by light.
1. Some photodermatoses have an internal cause and can be
inherited or immunity
based. Inherited photodermatoses are a rare group which
includes, for example, xeroderma pigmentosum (XP). Exposure to
UVA/UVB is associated with an increased
cancer risk in XP so
patients are advised to avoid all sources of UV, including CFLs
and unfiltered halogen bulbs.
Another group of photodermatoses have no known cause but are
increasingly thought to be based on immune responses. The part
of the spectrum that plays the main role is UV light, so the
main concern is with light sources that emit UV, such as CFLs.
The severity of these diseases varies widely between patients
and the amount of UV required to produce symptoms is also
- Polymorphic light eruption (PLE): Usually affects
females and flares up in spring or early summer and results
in an itchy, red, spotty rash on skin exposed to sunlight.
For most patients, artificial light sources do not induce
- Chronic actinic
dermatitis (CAD): This affects males over 50
years of age and results in sensitivity to various
allergens, to UVA, UVB and also
visible light for
some patients. UV from artificial light could induce the
disease in people with moderate or severe CAD.
- Actinic prurigo (AP): This uncommon disease happens
all year round but is particularly bad in spring and summer.
Skin exposed to sunlight develops itchy, red and inflamed
bumps. Severe cases may be at risk from CFLs or other
- Solar urticaria:
This skin disorder affects both males and females and if it
develops into a generalized urticaria, it can result in
anaphylactic shock, so it can be fatal. Severely affected
patients may be at risk from CFLs and unfiltered halogen
sources producing UV/visible radiation.
- Hydroa vaccineforme: This is a rare disease that
affects both sexes and produces blisters and scarring on
skin exposed to sunlight. Low energy artificial light
sources that emit UVA, can affect some patients.
erythematosus (LE): This affects all age groups in
both sexes and arises in people who produce antibodies
against the breakdown products of their own
patients are susceptible to agents that cause cell death.
Some drugs and factors such as UV (mainly UVB) exposure can
induce this disease. At least some patients are at risk from
long-term exposure to UV from CFLs and unfiltered halogen
- Porphyrias are a
rare group of diseases that are inherited but are also
induced by environmental factors and all relate to the
accumulation of the photosensitive pigment porphyrin within
the skin. Artificial light sources, including incandescent
bulbs, can cause skin reactions and even burns in the most
Some photodermatoses don’t have an internal cause but instead,
are induced by medicines or other chemicals. Many drugs can make
people sensitive to light. In the majority of cases, the drug
together with light starts
that make toxic levels of products. A smaller number of drugs
sensitize the immune system
instead. The effects depend on the drug but common symptoms are
changes in skin pigmentation, blistering or redness.
Some medical treatments exploit the photosensitizing ability
of chemicals and this is used for instance in
People undergoing anti-cancer photodynamic therapy are
intentionally given photosensitizers and they can have skin
flares if exposed to light so they could have reactions from
CFLs and LEDs. However, these patients are very aware that they
need to take precautions.
2. Photoaggravated dermatoses are a large and diverse group of
diseases that are made worse by light but also arise without
exposure to visible or UV light. Sunlight affects only a small
proportion of people with these diseases and the skin of most
patients seems to react normally to UV and
visible radiation. The
role of artificial light in these diseases is unknown but is
unlikely to be significant.
Table 4"Light related" skin diseases
5.2 Eye conditions
About 1.5 million people worldwide have some type of inherited
disorder where the retina
degenerates over time and, in terms of diseases, fall within a
range from Retinitis pigmentosa (RP) to macular dystrophies.
Patients with RP first lose night vision followed by lateral
vision and, in the late-stage of this disease, vision is
restricted to a narrow central cone. In macular diseases,
central vision is lost but side vision remains good. There are
also intermediate diseases where there is some loss of both
central and side vision. The age at which symptoms start, the
speed at which the disease progresses and the final outcome are
The effect of light on these patients depends on the specific
mutation that has caused the disease. For instance, two forms of
macular dystrophy (Ogushi disease and Stargardt disease) are
aggravated by light and Stargardt disease is particularly
affected by blue light, but this is not the case for other
diseases. Since patients don’t know which mutation they carry,
they are advised to avoid unnecessary exposure to light.
5.3 Other conditions linked to light flicker
The intensity of some light sources goes up and down regularly
and, if this oscillation is sufficiently slow, it is perceived
by the human eye as flicker. Flicker depends mostly on the light
source but is also affected by other factors such as the field
of view and whether or not the person is moving.
Obvious flicker has been implicated in conditions such as
lights that flicker too quickly to be noticed, can still cause
headaches and eye strain.
Early fluorescent lamps
flickered very noticeably but modern lamps are much better.
However, flicker varies considerably from one lamp to another
depending on the design so one cannot draw general
Light from LEDs is usually flicker-free, but some poor quality
LEDs do flicker, particularly if they are used together with a
There is no scientific evidence that non-skin conditions such
as Irlen-Meares syndrome, myalgic encephalomyelitis,
or HIV are worsened by exposure to light from CFLs. However,
experiments using other light sources and epidemiological
studies are needed before one can draw final conclusions.