There has been a debate about whether carbohydrate is essential for human survival. Some will argue that it is.
Glucose is a carbohydrate, a sugar, and the human body needs glucose to survive, so therefore it is essential. However, glucose can be obtained from protein and fat and it is not required for the body to obtain glucose from carbohydrate. Obtaining glucose from carbohydrate is usually the preferred method to obtain glucose rather than from protein or fat since it is easier, quicker and more efficient, actually a 'piece of cake.'
So therefore, glucose is essential for life since the brain cells die quickly without it, not to mention the other body cells die without glucose. However, to repeat this, it is important to understand that glucose does not have to be obtained from carbohydrate essentially. Glucose can be obtained from protein or fat by breaking down the protein or fat into glucose. Conversely it is impossible to obtain protein or fat from carbohydrate which is important to understand.
Fiber, a carbohydrate, is usually the only carbohydrate that is mentioned in literature about nutrition that is important in diet. "Not yet formally proposed as an essential macronutrient, dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake."  The minimum daily requirement has not been established and is widely debated in nutrition but the general consensus is that humans may need between "a minimum of 20–35 g/day for a healthy adult depending on calorie intake (e.g., a 2000 Cal/8400 kJ diet should include 25g of fiber per day).  While glucose can be converted from fat or protein, fiber can only be derived from carbohydrate, so therefore, fiber is the only carbohydrate that may be essential to humans. However, obtaining energy in the form of calories from soluable fiber is minimal at best [the body absorbs fewer than 4 Calories (16.7 kilojoules) per gram of fiber].  Some fiber is insoludable and therefore indigestible. Since the human body does not have the necessary enzymes to break down insoluble fiber for energy (glucose), fiber is not an important source for energy (glucose) in humans.
Carbohydrate is simply molecules of carbon, hydrogen, and oxygen. Carbo (carbon) + hydrate (water or H2O). Fairly simple, isn't it? There are absolutely no vitamins, minerals, amino acids (protein) or fat in carbohydrate, hence nothing essential for human survival. It is a common belief that plants are strictly carbohydrate, and this is where the misconception is. Yes, most plants are high in carbohydrate but they contain a great deal more than carbohydrate. Most plants are primarily made up of water and carbon but they also contain some protein, vitamins, minerals, and fat. Yes, plants usually are made up of all three food groups but primarily water and carbohydrate. For example, one cup of iceberg lettuce contains 76% carbohydrate, 16% protein, and 8% fat (not to mention some nutrients in the form of vitamins and minerals). So many conclude that carbohydrate is essential for human survival based upon their limited understanding of how we need to eat plants thinking that they are just carbohydrate, and are simply uninformed. To reiterate, plants in the form of vegetables and fruits contain all three food groups along with some essential nutrients with carbohydrate as the chief food group.
The fact is that carbohydrate is simply a wonderful perk since it is made up of different types of carbon, hydrogen and oxygen molecules that usually taste sweet. However, carbohydrate is not essential for human survival. Why is this? Our bodies are primarily made up of water, protein and fat.  Carbohydrate is simply used at its basic unit for energy. We burn glucose, a carbohydrate or sugar. Glucose is "the primary metabolic fuel for humans". Carbohydrate is simply different types of sugar, i.e., glucose, sucrose, fructose, lactose and the list goes on. The body converts all these different types of sugar into glucose which is the 'primary metabolic fuel for humans." Glucose is what the cells in our body use for fuel which can be obtained from carbohydrate. However, as previously mentioned, glucose does not have to be obtained from carbohydrate, as an "essential" carbohydrate, but can be obtained from either fat or protein.
While our body needs glucose for human survival, hence essential, (i.e., our brain cells begin to die without glucose in just a few minutes), we can obtain glucose by breaking either fat or protein through digestion into glucose for our energy and our brain cells. So do we actually need carbohydrate to make glucose? No. Carbohydrate is not necessary since we can convert fat and protein into glucose. However, it is way easier for the body to break carbohydrate into glucose. Piece of cake. It takes a lot more digestion to break down fat and protein into glucose, not to mention the side effects of only eating fat and protein. If we need quick energy carbohydrate is the preferred choice. But again, in terms of human survival, the bottom line is that if you were stuck on an abandoned planet or a desert island and you had to choose only two of the three food groups to eat for survival you better choose protein and fat since they are absolutely essential for human survival. Of course you would also need water, vitamins and minerals. But if you choose carbohydrate as one of the two food food groups and excluded either fat or protein you would eventually die since our bodies are made up of protein and fat. Protein and fat are essential for human survival while strictly speaking carbohydrate is not. The only carbohydrate that may be essential for human survival is fiber.
The difference between essential and non essential types of nutrition is clearly seen in this table:
Image courtesy of Click4Biology 
Carbohydrate (different types of sugar) is not essential for human survival, with the exception of fiber, which may be essential for human survival. Glucose, a carbohydrate, which can be obtained from protein or fat by digestion is strictly speaking the only essential carbohydrate.
Sugar = Rosacea Fire
The following is a quote from a widely accepted book on nutrition requirements for humans which says about the minimum requirement of carbohydrate:
"Although glucose is the most common source of energy available to cells, it is essential only in a few organs: the brain, the kidney (medulla) and the red blood cells. The adult brain requires about 140 g glucose/day and the red cells about 40 g/day. In the absence of dietary carbohydrate, the body is able to synthesize glucose from lactic acid, certain amino acids and glycerol via gluconeogenesis. Gluconeogenesis can supply about 2 mg/kg body weight per minute or 130 g/day."
While this source says "it could be said that the absolute minimum requirement for carbohydrate is about 50 g/day" it never establishes a minimum daily requirement for carbohydrate. 
You will be hard pressed to find a reputable source that says there are any essential sugars or carbohydrate. This is because carbohydrate contains no essential nutrient. Carbohydrate is energy, fuel. It is the preferred food to obtain energy in the form of glucose which the body uses. And I am not advocating a diet without carbohydrate. In fact I advocate a diet with complex carbohydrate but in a quantity and quality to control rosacea. Diet high in carbohydrate, particularly sugar is a rosacea trigger.
Here are some quotes to consider:
"Carbohydrates are not a requirement for survival as are proteins, essential fatty acids, vitamins, or minerals." 
"The major role of carbohydrates is to provide energy. Interestingly, carbohydrates are not considered essential." 
"For example, many amino acids can be made in the body via metabolism from other amino acids; as well, glucose can be made in the body from a number of different substances. So while these nutrients are essential for life and survival, it is not essential that they be obtained from the diet…..And while the above might suggest that dietary carbohydrates are essential, this isn’t the case." 
"First of all, it should be understood that the human body does not have an essential need for carbohydrates in and of themselves—in other words, there are no "essential" carbohydrates, as there are essential amino acids or fatty acids." 
"And though they are not a dietary requirement in the way that vitamins or essential amino acids are, it is difficult to eat without ingesting some carbohydrates, which are excellent sources of quick-burning energy." 
"Carbohydrates are not essential nutrients but are typically an important part of the human diet." 
"Strictly speaking, carbohydrates are not essential in that the body is capable of making some carbohydrates..." 
So what does carbohydrate have to do with rosacea? Carbohydrate is a rosacea trigger.
You can live without carbohydrate contrary to popular opinion and all those who debate this subject. Carbohydrate is a wonderful gift that makes eating delightful and sweet. But too much carbohydrate, especially sugar, can trigger your rosacea. Balance is the key and eating complex carbohydrate rather than the simple carbohydrate will improve your rosacea. For more info click here.
More information on Sugar and Carbohydrate Avoidance
 Click4Biology: Option A1 Components of the human diet.
The above researcher has shut this article down. However the wayback machine has the page in web history and the paper shown here on May 14, 2012. Too bad he closed the page down, since he should publish the paper. Here is a screenshot taken using the wayback machine:
 Essentials of Human Nutrition, Second Edition,
Jim Mann, A. Stewart Truswell, Editors, Part 1, Energy and macronutrients, Chapter 2, Janette Brand-Miller, 2.6.2, page 25,
Oxford University Press, 2002
 The Oxford Companion to Food by Alan Davidson
Oxford University Press, USA; 2nd edition (October 15, 2006)
 Pathophysiology: Functional Alterations in Human Health by Carie A. Braun and Cindy Anderson
Lippincott Williams & Wilkins; 1 edition (October 17, 2006)
 A Primer on Nutrition Part 1 by Lyle McDonald
 Carbohydrates - Real-life applications
Science Clarified, Real-Life Physics Vol 3 - Biology Vol 1
 Nutrition, Wikipedia
 Was Atkins Right? Scientists Say Carbs -- Not Fat -- Are the Biggest Problem with America's Diet by Ed Bruske
 Editors Web