Resident Evil 4 - All Yellow Herb Locations Guide

gamespot.com:

Resident Evil 4, much like the rest of the franchise, emphasizes the use of herbs to heal your characters. Yellow Herbs, in particular, tend to be very important, as they're the only way for you to increase your maximum HP. Here's our Resident Evil 4 Yellow Herbs guide to help you find all the possible health upgrades in the campaign.

The Resident Evil 4 Yellow Herbs can't be used on their own. Instead, you'll have to mix them with a concoction, preferably one that already has a Green Herb and Red Herb mixed in. This is because a Green and Red Herb combination will heal you to almost full HP and, when a Yellow Herb is added, you'll also be granted its permanent max HP boost segment.

Likewise, you'll want to pay attention to the Merchant's Trade panel, since he also sells a Yellow Herb in exchange for 3x Spinels (a currency obtained by completing requests). In any case, we've divided our Resident Evil 4 Yellow Herbs guide into several sections depending on the main zones and areas.

These are some of the Resident Evil 4 Yellow Herbs that can be found in the Village zone:

These are some of the Resident Evil 4 Yellow Herbs that you can pick up in the Castle zone:

If you've obtained all previously mentioned Resident Evil 4 Yellow Herbs, all while combining them with Green and Red Herb mixes, then you should have maxed out Leon's HP. This will earn you the «My Body is a Temple» achievement.

Whether or not you've maxed out Leon's HP already, you'll still be able to acquire additional Resident Evil 4 Yellow Herbs in the Island zone:

We'll continue to add more entries to our Resident Evil 4 Yellow Herbs guide, so stay tuned. Likewise, you can learn about other mechanics in our guides hub.