hyphen in anti-aging?

You're going to find a million different opinions on this, but to my mind when the compound word is an adjective, a hyphen should be used: anti-aging.

I checked on Google and found every possibility under the sun being used:  anti-aging, antiaging,  anti aging, and also, all of those possibilities with the preferred British English spelling ageing.

Two additional reasons to side with me and use the hyphen is that (1) antiaging looks really ugly, and (2) antiaging would trip up some people, particularly second-language learners, as to how to pronounce it correctly:  an-TEE-ah-ging [hard g] is of course incorrect.

Shawn's common sense answer is supported by the various American style guides. The general rule set forth by the Chicago Manual of Style (16th edition, University of Chicago Press) is that words with prefixes should not be hyphenated (see 7.85, Table 4 at page283). 

But CMoS also provides several exceptions to the general rule. When the prefix "anti" is added to a word beginning with a vowel -- for example, anti-inflammatory -- a hyphen is recommended. So "anti-aging" is the preferred spelling.  The other exception comes with words formed from proper names -- anti-Hitlerian.

I hope this helps.