You're likely referring to methyl salicylate, not "methyl salicylic". Methyl salicylate is the active ingredient in many topical pain relievers like aspirin and oil of wintergreen.

There are a few reasons why the internal use of methyl salicylate is limited to small quantities:

* Toxicity: Methyl salicylate can be toxic in large doses, causing serious side effects like nausea, vomiting, tinnitus (ringing in the ears), dizziness, and even liver damage.

* Aspirin-like effects: Methyl salicylate is a salicylate, and like aspirin, it can cause stomach upset, bleeding, and allergic reactions in some people.

* Overdose risk: It's easy to overdose on methyl salicylate if taken internally, especially with liquid forms.

* Better alternatives: For internal pain relief, there are safer and more effective alternatives available, such as ibuprofen and naproxen.

Therefore, internal use of methyl salicylate is limited to small quantities and only under the supervision of a doctor to minimize the risk of these potential adverse effects.

It's crucial to follow the recommended dosage and never exceed it without consulting a medical professional.