Holidaymakers will be "bearing all the risk" when overseas getaways return as they face little chance of refunds if they go into self-isolation.
Anyone who gets coronavirus symptoms at the time they are booked to go away is highly unlikely to get their money back when they cancel their holiday.
Package holiday firms and travel insurance will probably not pay out.
Alex Neill, of resolution service Resolver, said UK tourists needed to be aware they were "taking a risk".
"It is likely that new travel insurance policies won't cover you if you develop symptoms before going on holiday - and if the flight or packaged holiday isn't cancelled then you have no automatic right to compensation," she said.
"While it's important to the economy to support the travel industry, at this time it's the customer who is bearing all of the risk."
From Saturday, blanket restrictions on non-essential overseas travel are to be relaxed in the UK.
Travel companies said that holiday bookings "exploded" after ministers announced that restrictions would be eased.
Interest has been heightened by the announcement that dozens of countries will be exempt from travel quarantine requirements when holidaymakers return to England.
That should mean English holidaymakers returning from lower-risk countries will not need to self-isolate for 14 days when they get home. Restrictions remain for people returning to the rest of the UK.
Travel insurance gaps
People going on overseas getaways are strongly advised to take out travel insurance, which will still cover them for accidents, injury, lost luggage and so on. A European Health Insurance Card will also give access to state healthcare in the EU.
Some new travel insurance policies will now cover medical treatment for Covid-19 which has been caught while in a resort.
However, people who need to cancel a holiday because they or a loved one develop symptoms before going away, or are told to self-isolate at home, are highly unlikely to be covered.
Similarly, package holiday providers are unlikely to give a refund if a customer cancels in such circumstances. Some may allow rebooking, but that is not guaranteed.
There is a risk that people with holidays booked may try to ignore symptoms, or discard advice from contact tracers to self-isolate. The government has said people have a "civic duty" to quarantine if they receive a call from test and trace advisers.
"Most people would behave responsibly even if that meant losing their holiday, but I would also expect holiday and insurance companies to show a little compassion in these circumstances," Ms Neill said.
"Driving consumers to do the wrong thing can't be an unintended consequence of opening back up from lockdown."
Insurance companies argue that coronavirus is no longer an unforeseen event, so may not be included in cover.
The added protection usually available from booking via a credit card is also unlikely to be successful in such cases.
When holidays may be protected
There may be better news for people who already had a travel insurance policy bought or renewed prior to early March as they may still be able to make a claim for such a cancellation, but they should check their policy.
If the UK, or a destination country, re-introduces restrictions on travel as a result of a fresh outbreak, then a package holiday company or airline should refund holidays or flights that they then need to cancel.
However, refunds are unlikely if a 14-day quarantine rule is brought back in and a holidaymaker chooses to cancel as a result.
People taking a holiday within the UK will have to look at terms and conditions when booking for information about their cancellation rights.