Yeas ago, my son (3 years at the time, 33 years ago) was sick
with a bad cold. The doctor put him on a penicillin type antiobiotic. The next day he developed a rash, so the doctor thinking that it was an allergic reaction, changed his drug to erythromycin.
The next morning, my son had lots of redness and swollen eyes. I rushed him to another doctor who immediately gave him a shot of a penicillin derivative and put him back on the penicillin type drug.