What causes loss of smell during a cold?

[Frylock]

I have a cold (or something coldlike), but for about half of the day today have been able to breathe okay through my nose. Yet, I still have no sense of smell.

Which leads to my question. What is the cause of the loss of smell during a cold? Also is there anything I can do to help it return?

[Crazyhorse]

The virus damages the olfactory nerves. It’s usually (but not always) temporary.

Survey studies on the general population affected by olfactory
pathology show that disorders in the sense of smell
reach 19% of the population, ranging from 0.5% for anosmic
individuals and 17% for hyposmic individuals, depending on
whether you take international or local studies1,2; for absolute
loss of the sense of smell alone, the variation ranges
from 2% to 3%. Among the most frequent causes are the
common cold and flu…

Postviral olfactory dysfunction
is believed to be provoked by lesions in the olfactory
receptor cells.20,21 Consequently, it is a syndrome characterised
by sudden loss of the sense of smell after an upper
airway infection. When the infection is cured, the olfactory
alteration generally persists as the only nasal symptom,22
which can present different degrees of olfactory disorder
(hyposmia, anosmia, etc.).