Stinging nettles: “injecting a plethora of unpleasantness into your skin like a tiny hypodermic needle”

The Wildlife Trust tells me:

Each ‘hair’ or trichome is essentially a lengthy, brittle tube connected to a swollen sac of irritant fluid. They’re smothered all over the stems and leaves and every tube has walls stiffened with silica, making them as delicate as a sliver of paper-thin glass. Brush against them and the tip snaps off, injecting a plethora of unpleasantness into your skin like a tiny hypodermic needle.

And:

This complex venomous cocktail contains neurotransmitters such as histamine, serotonin and acetylcholine and acids such as formic, tartaric and oxalic, but it’s still not fully understood just how this elaborate brew functions to make a sting so prolonged.

Am I right in thinking this seems more potent now (in May)? I’m not sure, but there is variation based on the what I see in looking up the Influence of Harvesting Time on the Chemical Composition of Wild Stinging Nettle (Urtica dioica L.). Sadly, they didn’t give them a squeeze and rate the pain.