Image Alt tags--always include the targeted keyword?

[nicole.healthline]

Question for all the SEO's out there. Do you always include your target keyword in the image alt tag?

For example, if you had an article on osteoarthritis, and you included a photo of an old man, would you put "old man on a bench" or "old man suffering from osteoarthritis" -- even though you have no idea if the old man suffers from osteoarthritis?

[Unity]

I would use the keyword in a keyword phrase and limit to 2-3 words, so something like "Man with osteoarthritis" or "Osteoarthritis affects everyone".

Remember alt tags are also used for usability, so if someone say has a computer that reads them the on-page content (e.g. a visually impaired person) you want your content to clearly and accurately explain what's on the page.

[bradkrussell]

Agree with Davinia 100%. Write alt tags for the user - how would you BEST describe the image in a few words? I try to include a few keywords/phrases but if I have a page with 10 images I'm not going to include the same keyword(s) in every single image - probably around 50-80% of the images.

[MattAntonino]

As a photographer in a past life, what I did that did not work was use the same tag on every image in a post. That doesn't work.

What does work is variety.  Use the keyword, use related words, and use descriptive image words.  Say you had 3 images to keyword:

(image of an older guy on a bench) alt="osteoarthritis frequently affects elderly men"

(doctor, any health image) alt="healthy screenings can help reduce the symptoms of osteoarthritis"

(drug you're selling) alt="prevent joint pain and reduce osteoarthritis symptoms with X"

[Jeepster]

Related-ish question:

I have a site-wide banner on a website with a theme related to mine with the alt tag containing an exact-match keyword.

It's on 2,500 pages. Post-Penguin, am I inviting trouble? Should I play it safe and have it on, say, just a handful of pages -- or even just the homepage?