If you know what "red-eye" is -- and no, we're not referring to overnight flights -- then chances are you have light-eyed kids, grandkids or pets.

You see, when you use a camera with a flash, the light reflects off the back of the subject's retinas, causing their irises to look devilishly red in photos (and yes, as gross as it is, the red colour is in fact blood).

Some cameras, though, feature anti-red eye solutions – such as a double flash or in-camera software that fixes this common issue.

Or, if you want to try and avoid red-eye altogether, whenever possible take your photos with natural light, such as outside during the day (read: no flash), to avoid this common problem.

The most popular way to lick this problem, however, is via free computer software.

Remove red-eye with Flickr

Let's say you have a collection of photos on your PC and many of them have the dreaded red-eye. Many software packages today -- including Windows Photo Gallery, Google's Picasa and Adobe Photoshop Express -- have one-click red-eye fix, but some handle it better than others.

Here's how to pull it off in Flickr, the popular online photo gallery.

1. If you haven't done so already, create a free account then log in with your username and password (your Yahoo! Mail or Messenger ID will work, too).

2. Upload photos to your online gallery by selecting specific ones from your computer. Find one that has kids or pets with red-eye.

3. Above the picture, click on the tab that says Edit Photo. This will launch Picnik, a web-based photo editing service that has partnered with Flickr.

4. The last edit tab says "Red-Eye." Click this. You're now asked if you need to fix a "Human" or a "Furball." Select the relevant one and then click on the centre of the eyes of the subject(s) and you should see the red-eye removed. If you like what you see, click Save.

That's it!