The advertising watchdog has banned two adverts for "exploiting health-related anxieties" during the coronavirus pandemic.
Manchester-based clinic PCK Skin was reprimanded for offering prescription-only vitamin injections, while dairy company the Chuckling Goat Ltd broke the rules by implying its "gut health" products prevented, treated or cured disease.
Both adverts promoted the "immunity-boosting" benefits of their products to fight against viruses, the Advertising Standards Authority (ASA) said.
The adverts are not permitted to appear again "in the same form".
The Chuckling Goat, based in Wales, ran poster adverts on the side of buses in Yorkshire and Reading in April directing consumers to its website which contained pages on flu and viruses, the ASA said.
The poster adverts said: "What's your best defence against any virus? Boost your immune system" followed by "Quick and free – live gut health advice".
In a ruling, the ASA said: "We considered that because of the context in which these claims appeared, namely on the 'viruses' and 'flu' web pages, alongside featured food products, consumers would understand that those products listed could help to fight against viruses and the flu by boosting immunity and improving gut health.
"We concluded that the claims implied that their food products prevented, treated or cured human disease, which was prohibited under the code.
"The ads must not appear again in the same form."
Similarly, PCK Skin's trading division SkinSpaceUK sent a promotional email in March offering "40% OFF! IN THE FIGHT AGAINST VIRUSES!" as it promoted vitamin D and vitamin B12 shots.
The ASA said all licensed vitamin D and vitamin B12 injections were prescription only and therefore the advert breached its rules by promoting them to the public.
It added in its ruling: "In the context of a global pandemic of coronavirus/Covid-19 consumers were likely to understand that "VIRUSES" included coronavirus.
"Therefore the ad gave the impression to recipients that the vitamin D and vitamin B12 injections being sold were effective in helping to prevent or treat coronavirus/Covid-19."
It noted that none of the products were indicated for the prevention or treatment of coronavirus.
PCK Skin had argued the email was sent only to their client database and that a full medical consultation was always carried out to determine if a person had a vitamin deficiency prior to any treatment.
But the ASA said it was promoted to customers and not medical professionals, adding: "The ad promoted prescription-only medicines to the general public and therefore breached the code."
The ASA said both cases were "fast-tracked" as part of its focus on "prioritising and tackling ads that exploit health-related anxieties during the crisis".