[Digital drawing created on my phone in an old, no-longer-supported sketch app.]
This is a microscopic curse particle. It might not seem like much, but the refraction rate of this creature/electromagnetic beastie is such that any positive energy that strikes it (even at the photon level) is split into dark **anti-light**, which causes illness and unhappiness. Chocolate can help protect you---particular in SHAKE form---from the majority of the effects of the "Little Thing," but to be cured completely, you'll need an electro-spiritual cleansing from a properly attuned Micro-Magical Mage. (They aren't cheap...)
---Richard F. Yates (Holy Fool)