Guava (Psidium guajava) is a tropical fruit native to the Americas and now grown throughout Southeast Asia. In Thailand it is usually eaten while still green and crunchy, with pale flesh and a mild, slightly tart taste, often dipped in a mix of sugar, salt and chili.
That fruit-stall habit has become a packaged snack. Doi Kham Savoury Guava with Chinese Apricot Flavor is 78% guava, tossed with sugar, Chinese apricot (plum) powder, iodized salt in both chunky and fine form and a pinch of chili. The result is sweet, salty and sour at once, a combination Thai snackers know well.
Guava itself is not a common allergen. This snack also lists INS 223 (sodium metabisulphite) as an antioxidant, a sulphite that people sensitive to sulphites will want to know about.

