Paris Hilton and Lindsay Lohan have long been as famous for their personal problems as they have been for their Hollywood careers. But could their successful clothing, perfume, and accessories lines finally be seeing the effects of the ladies' continued troubles with drugs and the law?

After pleading guilty to cocaine possession in Las Vegas on Monday, resulting in year of probation, a $2,000 fine and 200 hours of community service, Hilton was detained for questioning by officials at Tokyo airport where she had flown for a business trip.

"Paris was contractually bound to her business trip and didn't want to let down her brands and many Asian fans. She intended on fulfilling her contract and is trying hard to do the responsible thing, but this is beyond her control," Hilton’s rep said in a statement.

Apparently Japan didn't think pleading guilty to cocaine possession was beyond her control. Hilton was barred from entering the country. She then canceled planned appearances in Malaysia and Indonesia to promote her lines. Those countries, too, have strict anti-drug laws.

Meanwhile, Lohan’s future is under speculation as she awaits a court hearing on Friday which will determine whether or not she should spend more time in jail for failing two court-appointed drug tests. This comes just weeks after being granted an early release from prison and rehab.

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According to Hollywood image consultant Michael Sands, Lohan and Hilton may have reached the point where they think all PR is good PR, and are numb to the consequences.

“Both Lindsay and Paris are drama queens still vying for media attention in hope of keeping them in the public view, but their brands are going to take a serious hit,” he said. “The buying public does not support illegal drug addicts, foreign countries are not going to let them in because drug laws will rule over any ‘fame’ they claim to have. This is all going to come back to haunt them for many years, whenever they travel abroad they will be questioned about their drug abuse, searched and publicly humiliated. At least for the next couple of years, these ‘stars’ are not insurable for other projects. They are not a good image for any demographic.”

But traveling overseas isn’t going to be the only challenge the stars will face.

“They will most likely have issues at border crossings for the next 10 years,” said Florida-based attorney Raymond Rafool. “And depending on the state, drug offenses cause an automatic driver's license suspension. Rental car companies may preclude car rental for years. Drug offenses will affect a person's insurability such as health insurance and life insurance. Everyday life can be affected and charity work if associated with children.  Certain agencies and churches may have policies which preclude accepting assistance from people convicted of felonies or drug charges.”

Despite the negative attention surrounding the women in recent weeks, according to some, their most popular products are still selling.

A sales associate at Sephora in Beverly Hills told Pop Tarts that Lohan’s tanning line “Sevin Nyne” was a hot seller throughout summer. A rep at trendy Los Angeles boutique Kitson on Robertson Boulevard said that LiLo’s leggings line, 6126, also continues to be very popular –although not necessarily because of Lohan’s association.

“It sells because of the style and price of the goods, not because she is behind it. In truth not many people know 6126 is her line,” Director of Operations Dean Khial explained.

Hilton’s string of fragrances are only sold in select Macy’s department stores. Associates at a Los Angeles area Macy’s stores said the fragrance was still “doing very well” despite her cocaine confession.

So when will the world stop supporting them, and in essence, fueling their bad habits?

“I think most people are pretty disgusted with them. If they ever want to be associated with anything quality, they'll need to clean up their brand,” marketing expert Penny C. Sansevieri said. “They need to do this publicly. Admit their shortcomings, show their human side. People understand being human, but I do believe this will be the last time they can dip into the public sympathy well.”

Branding expert Dan Schawbel believes that while the troubled twosome have the potential to resurrect their image, they need to straighten up fast.

“They can recover ... even despite their drug scandals, because they are name brands that people care about,” Schawbel said. “[But] if they continue to be involved in scandals, then they will eliminate future revenue and career opportunities. Tiger Woods lost sponsors with his scandal and there will be more companies that decide to represent other celebrities who have strong morals.”

Additional reporting from Deidre Behar