What Were The Conditions In The Trenches Like In World War One?

Overall life in the trenches in World War One was pretty grim. Estimates say that a third of Allied casualties on the Western Front were sustained in the trenches, a large number of said casualties were due to disease.
Trenches were crowded and were, of course, very dirty especially after heavy rainfall when the trenches could quickly be filled with muddy water that could sometimes lead to the trench walls collapsing.
When the weather was warmer this aided the spread of diseases such as cholera and typhus.
These kinds of unsanitary conditions could sometimes lead to a medical condition called Trench Foot. This was a fungal infection caused by the cold, wet conditions and could sometimes turn gangrenous.
Rats proved to be the biggest carrier of disease, millions infested the trenches and feasting on human remains. The rat infestation remained throughout the duration of the war contaminating food and spreading infection.
On top of the infestation of rats, soldiers also had frogs and lice to contend with. Lice would live and breed within the mens clothes and may eventually cause Trench Fever, a disease that could take up to twelve weeks to recover from. Other issues included frogs and nits.
Due to rising demands and the current emergency rationing, decent food quickly become scarce within the trenches. Much of the food was stale and most soldiers barely ever had a hot meal. This sometimes lead to yet more health issues including malnutrition or severe diarrhea.

In World War I, the "trenches" were literally trenches dug into dirt or mud to shelter soldiers while they were firing at the enemy. Both sides used trenches in the fighting.
Trench warfare was primarily a defensive tactic, placing soldiers low in the trench for protection, installing barbed wire in front of them in more modern times, and then allowing the soldiers to shoot at the enemy. Trench warfare has been used militarily since Roman times, although it came into widespread use in World War I.
The trenches were, of course, dirty. They could often become crowded, so any kind of wound sustained in the trenches was likely to become infected, whether it was sustained in battle or from opening a can. Shell fragments often carried dirt or other debris into the wounds they created. Infection and gangrene claimed a much higher percentage of fighting men’s lives than did actual deaths directly from fighting. Antibiotics had not been invented in World War I, so palliative care was about the only treatment that could be given.
Besides the direct effects of wounds, the indirect effects of many men in close, dirty quarters meant that common diseases like colds and the flu could spread quickly. When it rained, the trenches became low-level marshes, filled with inches of dirty water that made soldiers susceptible to fungal infections now known as trench foot and trench mouth. Parasites like lice, fleas, and weevils were everywhere, and they could spread other diseases. Dysentery, typhus, and cholera could spread quickly during warm, wet weather, forcing many of the troops into the hospital even if no bullets had ever passed their way.
Some trenches were dug quite deep, and then fortified with lumber to make things a little drier and more homelike. But in general, these were developed to cover short distances and be a temporary defensive position for troops before moving on to a new battlefield, so there was little in the way of creature comforts.

They were awful. There was rats eating rotting bodies, producing 900 babies from just one couple. Lice was embedded in the uniforms and hatched, producing trench fever. Hygiene was terrible, so if you were wounded that usually got infected and typhus and gangrene were common. In the summer, it was stifling and almost unbearable to live in. You had to be sweating in your uniform all day, smelly and uncomfortable. In the winter it was even worse...sometimes it rained so much that the trenches filled with muddy water, which made the hygiene even worse. A few times, the trenches collapsed inwards from the constant rain and it caused chaos for all the men. When it snowed or was icy, it was bitterly cold and men probably died from hypothermia. Yet men still had to Go Over, face the enemy and watch their friends die on top of everything else. I have solid respect for them!

your dad makes betefacts and hees dead

Trenches were built to move across the war field without being noticed and since it was below the ground level the solders were able to move safely through these and it served as shelters when there was heavy firing from the enemy side.

Horrendous hell on earth ankle deep in freezing water death and decay surrounding you confusion and hunger then the imminent order up n  over meaning out of the trench and charge the enemy facing artillary and machine gun fire and mines to an almost certain death.

The trenches were the front line of the war and as such the most dangerous place to be. They were also very uncomfortable, though conditions varied. Squalor was always inevitable, with so many men living together in such a constrained space. Latrines, discarded food and waste and inability to wash or change clothes for weeks at a time created conditions of severe health risk, further exacerbated by numerous rats and lice spreading disease. Disease was also spread by the maggots and flies feasting on the decomposing corpses. Weather contributed to the unpleasantness, with rain causing trenches to flood, sometimes up to waist height. And the winter in 1916-17 in France and Flanders was the coldest in living memory. Men suffered from exposure, frostbite and trench foot - a wasting disease of the flesh caused by the foot being wet and cold and constrained into boots for days on end; you could be crippled this way. As well as being dangerous during military action, there was always the threat of getting caught by a sniper anytime. Then there was the loud shelling that could lead to 'shell-shock', and the miseries of poison gas attacks. Trench life was generally tedious, prone to boredom and was hard work, with the trenches requiring constant building and repairing. Discipline was necessarily strict - a man could not leave his post without the permission of his immediate commander.