Tests recently went on sale at Lidl.
The World Health Organisation says people could be making "inappropriate decisions" if they rely on the result from an antigen test.
The tests, which recently went on sale in Lidl, get a result quicker - but aren't as accurate as other types such as PCR.
The Chief Medical Officer has strongly recommended against people buying and using antigen tests themselves.
Dr Margaret Harris from the WHO says people could get false reassurance from the result:
.
The World Health Organisation says antigen tests are a useful tool that can be used in some settings.
Dr Harris says they can play a role in some instances:

Naas Nurses to begin Work-To-Rule
IFA Protest Targets Minister Heydon's Newbridge Office Over Bord Bia Chair Controversy
Damning Audit Reveals €1.6m Moone-Timolin Cycleway As Safety Time Bomb
Five Kildare Special Schools Included In New Scheme Bringing Therapists Directly Into Schools
Give Gardai Scramblers To Enforce Law On Illegal Bikes, Says Kildare Garda Member
Labour Urges EuroGiant To Give Workers Clarity As Job Fears Grow
Panda Raises Bin Costs In Parts Of The Capital, Leaving Door Open To Wider Hikes Across Leinster
Major Drainage Project Serving Kildare Moves To Early Procurement