Certain types of light bulbs are being phased out across Europe
A European Union ban on the manufacture and import of 100 watt and frosted incandescent light bulbs, in use since the 19th Century, has come into force.
The EU wants the bulbs to be replaced mainly by longer-lasting compact fluorescent lamps.
The Energy Saving Trust says fluorescent lighting uses 80% less electricity than traditional bulbs.
But campaigners say the new bulbs can trigger health problems in people with light-sensitive medical conditions.
They are also more expensive than traditional bulbs, although save money in the long run.
The ban will be extended to all incandescent bulbs by 2012.
The Energy Saving Trust said energy-saving bulbs could also cut the average UK household's annual energy bill by up to £37 and save 135kg of CO2 each year.
The incandescent bulb is little changed since it was first produced by Thomas Edison in the 19th Century.
Some shopkeepers have reported that many people were stockpiling 100W bulbs ahead of the ban.
Any remaining supplies can still be sold in shops.
But there are health concerns over the use of the new energy-saving bulbs.
Fluorescent light is said by some lupus sufferers to trigger painful symptoms. It has also been linked to migraines and an increase in the risk of seizures for people with epilepsy.
David Price, of Spectrum, an alliance of charities working with people with light-sensitive health conditions, said the government was "disregarding" public concerns over the usage of the new generation of bulbs.
He said: "Health is important and it should come over anything else, but they're not looking after ours.
"They're not listening to the public and aren't talking to the actual sufferers."
Brenda Ryan, 56, from the Isle of Wight, suffers from an extreme form of lupus and said the growing presence of energy-saving fluorescent light bulbs in the UK had forced her to stay indoors.
She said exposure to the new light bulbs led to a reddish-purple rash on her skin and "continuous vomiting", which could last for several weeks, making her "completely dependent" on her husband.
Brenda Ryan suffers illness when exposed to energy-saving bulbs
The Department for Environment, Food and Rural Affairs said it was working closely with organisations representing the 36,000 people in the UK who have a "special health interest".
It added that EU health experts "concluded that there is not enough evidence to suggest that modern lamps can aggravate epilepsy or migraines".
The Department of Health said EU health experts had recommended that a "small percentage" of people with light sensitive conditions should use so-called "double-envelope" fluorescent lights.
The Department of Health said the experts believed the double-envelope bulb could "largely or entirely mitigate the risk of aggravating the symptoms of light-sensitive individuals".
INCANDESCENT LIGHT BULB
Traditional 100W light bulb
Glass mount carries electrical connection from base to the filament
Electric current passes through the filament which heats up and emits light
Inert gas inside bulb protects filament and improves luminescence
COMPACT FLUORESCENT LAMP
'Energy saving light bulb'
Electrical current emitted from electronic 'ballast'
Current flows into gas filled tube causing it to emit invisible ultraviolet [UV] light
UV light causes phospor coating inside the tube to emit visible light
Requires 20-23 Watts of electricity to generate same amount of light as a traditional 100 Watt bulb