BALTIMORE (Stockpickr) -- U.S. markets recovered from most of their losses on Thursday, rebounding after the big market averages started the day by selling off more than 1.5%. The declines may have been tempered by the time the closing bell rang on Thursday, but the message here is still pretty clear: The volatility isn't over in 2015.

And that makes it especially important to avoid underperforming stocks right now. They could be toxic to your portfolio.

To find out which stocks are showing red flags ahead, we're turning to the charts for a technical look at five big "toxic stocks" you don't want to own.

Just to be clear, the companies I'm talking about today aren't exactly junk. By that, I mean they're not next up in line at bankruptcy court. But that's frankly irrelevant; from a technical analysis standpoint, sellers are shoving around these toxic stocks right now. For that reason, fundamental investors need to decide how long they're willing to take the pain if they want to hold onto these firms in the weeks and months ahead. And for investors looking to buy one of these positions, it makes sense to wait for more favorable technical conditions (and a lower share price) before piling in.

For the unfamiliar, technical analysis is a way for investors to quantify qualitative factors, such as investor psychology, based on a stock's price action and trends. Once the domain of cloistered trading teams on Wall Street, technicals can help top traders make consistently profitable trades and can aid fundamental investors in better entry and exit points.

So, without further ado, let's take a look at five "toxic" stocks to sell.

Enterprise Products Partners

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Underperformance has been nothing new for shareholders of midstream energy stock Enterprise Products Partners (EPD) - Get Report . This $51 billion stock has lost almost 30% of its market value since the start of this year. The bad news is that shares could have even further to fall as we enter the final stretch of 2015.

Enterprise Products Partners is currently forming a bearish descending triangle pattern, a price setup that's formed by horizontal support down at $25, and downtrending resistance to the upside. Basically, as shares of Enterprise Products Partners bounce in between those two technically significant price levels, they've been getting squeezed closer and closer to a breakdown below that $25 price floor. If $25 gets violated, then look out below.

Relative strength, which measures Enterprise Products Partners' price performance vs. the broad market, is another red flag to watch here. The lower highs in our relative strength line tell us that this stock is still underperforming the S&P 500 right now. As long as that relative strength downtrend keeps pointing lower, this stock's price action should continue to be toxic.

Shares are testing that $25 level this week. If it gets busted, it's time to sell.

Etsy

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We're seeing the same setup in shares of recent IPO Etsy (ETSY) - Get Report . Like EPD, Etsy is forming a pretty textbook descending triangle pattern. In fact, this stock has essentially been going nowhere but down since it first started trading back in April. From here, $13 support is the key price level to watch out for.

Why all of the significance at that $13 level? It all comes down to buyers and sellers. Price patterns, such as this descending triangle pattern in Etsy, are a good quick way to identify what's going on in the price action, but they're not the actual reason a stock is tradable. Instead, the "why" comes down to basic supply and demand for Etsy's shares.

The $13 support level is a price where there has been an excess of demand for shares; in other words, it's a spot where buyers have previously been more eager to step in and buy than sellers have been to take gains. That's what makes a breakdown below $13 so significant -- the move means that sellers are finally strong enough to absorb all of the excess demand at that price level.

Like with any breakout trade, it's important to be reactionary here. Big downside in Etsy doesn't become a high-probability trade until sellers are able to knock this stock below our $13 support level.

Nordic American Tanker

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Meanwhile, 2015 has actually been a stellar year for shares of $1.4 billion tanker company Nordic American Tanker (NAT) - Get Report . Year-to-date, Nordic American is up more than 54%, leaving the rest of the broad market in its dust. But if you own this stock, it might be time to think about taking some gains off the table.

That's because Nordic American Tanker is currently forming a double top pattern, a bearish reversal setup that looks just like it sounds. The double top in NAT is formed by a pair of swing highs that peak at approximately the same price level. The sell signal comes on a violation of the trough that separates those two price highs. For Nordic American Tanker, that's support down at $12.50.

The side-indicator to watch right now in Nordic American Tanker is momentum. Our momentum gauge, 14-day RSI, has been rolling over, making lower highs on the price action's pair of peaks. That's an indication that down days are outpacing up days in this stock. If $12.50 gets broken, then this outperformer becomes a sell.

Boston Properties

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The price action in shares of commercial property REIT Boston Properties (BXP) - Get Report has been a little bit easier to decipher lately. In other words, you don't need to be an expert technical trader to figure out the primary trend in Boston Properties. Since the start of this year, BXP's price chart has been moving down and to the right in a well-defined downtrend.

Boston Properties' downtrend is formed by a pair of parallel trendlines that identify the high-probability range for shares of this stock to remain stuck within, with shares moving lower every time this stock has hit its head on the top of the channel. Every test of the top of this stock's price channel has been a great selling opportunity, and shares are pressing up against that trend line resistance level again this week From here, it makes sense to sell the next move lower.

Waiting for that bounce lower before clicking "sell" is a critical part of risk management for two big reasons: It's the spot where prices are the highest within the channel, and alternatively it's the spot where you'll get the first indication that the downtrend is ending.

Remember, all trend lines do eventually break, but by actually waiting for the bounce to happen first, you're confirming that sellers are still in control before you unload shares of Boston Properties.

Novo Nordisk

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Last up on our list of toxic price setups is $114 billion Danish pharmaceutical stock Novo Nordisk (NVO) - Get Report . Even though this stock has enjoyed some excellent upside this year, climbing 30% higher since January, this stock has spent most of the last six months forming a classic bearish reversal pattern. A violation of support at $54 is our sell signal in Novo Nordisk.

Novo is showing off a classic head and shoulders top, a bearish reversal pattern that indicates exhaustion among buyers. The head and shoulders pattern is formed by two swing highs that top out at approximately the same level (the shoulders), separated by a higher high (the head). The sell signal comes on a move through Novo's neckline -- that's at the aforementioned $54 price tag.

Lest you think that the head and shoulders is too well known to be worth trading, the research suggests otherwise: a recent academic study conducted by the Federal Reserve Board of New York found that the results of 10,000 computer-simulated head-and-shoulders trades resulted in "profits [that] would have been both statistically and economically significant." That's a good reason to keep a close eye on Novo Nordisk's $54 level here.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.