Taken from the Wikipedia page:

Trombiculidae (pronounced /trɒmbɨˈkjuːlɨdiː/) is a family of mites called trombiculid mites (also called berry bugs; harvest mites; red bugs; scrub-itch mites; and aoutas.^[3]   In their larval stage, those species which bite their host and "causes intense irritation"^[4] or "a wheal, usually with severe itching and dermatitis,"^[5][6] are called chiggers.^[7]   Trombiculidae live in the forests and grasslands and are also found in low, damp areas where vegetation is rank such as woodlands, berry bushes, orchards, along lakes and streams, and even in drier places where vegetation is low such as lawns, golf courses, and parks.^[8]

They are most numerous in early summer when grass, weeds and other vegetation are heaviest. In their larval stage they attach to various animals, including humans, and feed on skin, often causing itching. These relatives of ticks are nearly microscopic measuring 0.4 mm (1/60 of an inch) and have a chrome-orange hue.^[9][10] The (best known) species of chigger in Northern America^[11] is the hard-biting Trombicula alfreddugesi of the south-eastern United States and humid mid-west^[12] and Mexico…

It’s that time of year again, friends, when you’re minding your own beeswax in the great outdoors, & then you suddenly have a burning itch in your leg, you look down and there is a tiny red dot…  Darn, chiggers! 

I used to think that these bugs would actually drill down into your skin, then you put nail polish over the site and they suffocate, then the burning would stop.  Well, that’s not quite it.  It turns out that the chiggers are actually only interested in eating your skin cells.  They attach to you, and inject enzymes that break down your skin cells, then suck up that tissue through a tube.  This tube is created by your body trying to protect itself by hardening the skin cells around the bite area.

Itching from a chigger bite can develop 24-48 hours after the bite, and the chigger can remain attached for 3-5 days before dropping off to take on it’s next stage in life. 

It is difficult to treat chigger bites due to the number of factors involved in a chigger wound:

• Mechanical damage
• Allergy response
• Immune response
• Possible bacterial infection / subject to local influences

Each person will respond with a different combination of these things in their reaction to the chigger bite.  So some treatments will work better for some than for others.  The toxic enzymes and the tube (stylostome) can remain in your skin for 7 days or more. 

Here are some ideas to help treat chigger bites:

See your doctor if there are signs of infection (redness in skin around wound, heat, swelling) or severe dermatitis.

Reducing itching:

• Over the counter topical corticosteroids / antihistamines
• Hot shower / bath
• Topical anesthetic

Getting rid of the chiggers:

• Soaking the bite site in Epsom Salt water
• Wiping the area with isopropyl alchohol

Two over-the-counter meds:

• Chigarid, forms a protective barrier over the wound
• Chiggerex, a soothing cream

Covering the wound with clear nail polish is a home remedy that I have actually found to work at times.  While I now know that it isn’t due to suffocating a burrowing chigger, it is possible that sealing the bite from the air might be effective – or it might be removing or neutralizing the stylostome / tube & toxic enzymes present in the bite.