My DH always ends up with a second line on his lateral flow tests but they only appear after the half hour time limit.
This first happened weeks ago when we left his on the worktop overnight and noticed a line the next morning. But it seems to happen every time we haven’t chucked it out and today’s one is actually darker, although still didn’t appear within the time limit.
The rest of the family have never had even a squinter of a line even when left overnight.
Having looked online after the first time it seemed to suggest that it could be totally disregarded unless it appeared within the time limit. Yet it just seems very odd that it’s always him and never me or the kids. We all test twice weekly.